Paul wanted the Romans not to be complascent about their faith - not to think they had 'arrived' and therefore it didn't matter how they lived their lives because they were already 'saved'.  He understood that Christ was to return and judge everyone and thought it would be soon (in earthly terms), so he was warning them to keep that in mind.

Seeing we don't know when Christ will come again to judge us, we must also live as if it is going to happen 'soon'.

Quest Study Bible note p 1567.  Paul and other New Testament writers taught that Christ would come again 'soon'.  Their language could be understood in terms other than approximate measures of time.  Christ's return is 'soon' from a prophetic perspective.  This perspective isn't concerned with when things will happen as with what will happen. Timing is less important than what is next on God's salvation program.  From this perspective, the next event is the second coming of Christ.

V 12.
It is far on in the night; day is near. Let us therefore throw off the deeds of darkness and put on our armour as soldiers of the light.
NLT.  The night is almost gone; the day of salvation will soon be here.  So don't live in darkness.  Get rid of your evil deeds.  Shed them like dirty clothes.  Clothe yourselves with the armour of right living, as those who live in the light.

It seems to me a great analogy to talk about life without Jesus as being in the night or in the dark.  It's in the dark that those who want to commit crimes prefer to operate - or at least they like to work when they'll not be noticed - and at night or in the dark is a good time for that (well, I imagine it is! I haven't so far had the need to be working at something when I didn't want to be seen - except for playing Santa on Christmas Eve and filling the children's stockings - or, in our case, pillow cases!).  We talk about someone being in the dark about something - that is, they are in ignorance.  And without Jesus, we are ignorant of so much.

Living in the light is much more healthy. And the healthiest we can get is when we live in the Son-light - the light which Jesus brings into our lives.  When my mother was suffering from depression I took her to see a wonderful phychiatrist.  One of the things he asked me to do was to change all her light bulbs to fluorescent bulbs and to get her outside in the sunshine as much as possible.  He told me that in some cases of depression, that's all that is needed to keep people well!  I remember reading a book where Catherine Marshall wrote about a severe illness she had and how it was only when she spent time out in the sunlight that she started to get well again.  (Can't remember the title of the book, or the nature of the illness - sorry.  You'll have to read all her books to find out which one it was!!)  Those are examples of the benefits of physical sunlight, but the benefits of spritual son-light are even greater. It is when we live our lives open to Jesus and to all scrutiny that we will be living fully as God intends us to live.

Paul talks about the armour of God in Ephesians 6: 10 - 18 and talks about fighting against the evil rulers and authorities of the unseen world, against those mighty powers of darkness who rule this world.... (NLT).  In Ephesians Paul describes the armour as:
Belt - truth
breastplate/coat of mail/body armour - righteousness (NLT, NIV) integrity (NEB)
shoes - the gospel of peace, to give you firm footing (NEB), readiness that comes from the gospel of peace (NIV), the peace that comes from the Good News, so that you will be fully prepared (NLT), the readiness to announce the Good News of peace (TEV)
shield - faith (to quench all the flaming arrows of the evil one - NEB)
helmet - salvation
sword - the Word of God, given by the Holy Spirit
This is the armour of right living - the kind of living that causes God to delight in his children.

V 13.
Let us behave with decency as befits the day: no revelling or drunkenness, no debauchery or vice, no quarrels or jealousies!
NLT. We should be decent and true in everything we do, so that everyone can approve of our behaviour.  Don't participate in wild parties and getting drunk, or in adultery and immoral living, or in fighting and jealousy.
TEV.  Let us conduct ourselves properly, as people who live in the light of day; no orgies or drunkenness, no immorality or indecency, no fighting or jealousy.

Here is the practical working out of when we are wearing the 'armour of God' - the kind of behaviour that results when we are living to please God and not to please only ourselves.  It was the kind of life-style that set the early Christians in Rome apart from the culture they lived in., and to some extent sets today's Christians apart too.  The church has been very dilgent in telling us no this and no that - so much so that, at least in some denominations, we have earned the reputation of being against anything that makes life 'fun'!  One lady who attends one of my church's outreach groups was heard to say, "Don't try to get me to be a Christian. Christians have no fun."  (This, in an atmosphere of chat, laughter and enjoyment, organised by people who are friendly, laughing and joking much of the time and who surely must seem to be enjoying life!)

It seems to me that Christians have been good at speaking out against immorality, adultery, orgies, drunkenness and debauchery in the wider community and, to a lesser extent, within the church.  But what about quarrels, fighting and jealousy?  How often do these behaviours happen within our church families?

As Christians, we must be seen to be living 'right' - or we give God a bad name!

V 14.
Let Christ Jesus himself be the armour that you wear; give no more thought to satisfying bodily appetites.
NLT.  But let the Lord Jesus Christ take control of you, and don't think of ways to indulge your evil desires.
NIV. Rather, clothe yourselves with the Lord Jesus Christ, and do not think how to gratify the desires of the sinful nature.
TEV.  But take up the weapons of the Lord Jesus Christ, and stop giving attention to your sinful nature, to satisfy its desires.

Giving up things that we physically crave for is not easy to do.  I have problems with food and eating and it is almost as hard for me as it is for someone to give up smoking. (Yes, I know food is OK and a 'blow-out' every now and again doesn't hurt. But not a 'blow-out' every day!!)  It is only when I spend time focused on Christ or on a task he has given me that I have any chance of controlling this 'addiction'.  One answer to my prayers for help was the suggestion that every time I feel a craving coming on, I stop and pray.  Well, sometimes I do and sometimes I don't!  Another way of 'clothing ' myself with the Lord Jesus Christ is when I surround myself with Christian music and Christian books and magazines to read - as well as enjoying the fellowship of other Christians in social activity, 'good works' and in worship together. He has led me to other practical ways of help as well. Praise him!

When we spend much of our time thinking about our physical desires, it becomes very hard to be moderate or to give up those that may damage us or that are downright immoral.  When our attention is focused on our relationship with God, we have less thinking time to spend on ourselves.

New Bible Commentary, p 1153. ...we are to surround ourselves with the Lord Jesus Christ in such a way that all we do is done through him and for him, and we are not even to give thought to any of those sinful desires that stem from this fallen world..