Don't lie to me now!

I've been meditating on Col 3:9,10: Do not lie to one another, since you have put off the old man with his deeds, and have put on the new man who is renewed in knowledge according to the image of Him who created him.

Why in the world would Paul tell us not to lie to each other. Isn't that fairly obvious that we shouldn't do that? But I find it more interesting that he says do not lie SINCE you have put off the old man with his deeds...

The old man's deeds were the way of death, the new man lives the way of life.

What ways have I been thinking and being death, instead of being and breathing life....