Can't really say I've thought much about it, to be honest. I've never smoked, so I've never had to deal with it. Have had plenty of other stuff to, though! Everyone has their own problems, own troubles, and it's easy to point to others and judge. Smoking for some, alcohol for others, food...sex...shopping....idols...you name it. And it I think we struggle in our "western" culture as some things are seen as more socially acceptable than others, and these things we sweep under the rug a bit.
I think, perhaps it comes down to this: God loves you, and probably wants you to care for your body...after all, we are the temple for the Holy Spirit to dwell in. But, our sanctification and walk with God is something that progresses over many years. It can be painfully slow at times. I think we need to stop feeling such condemnation for ourselves and the things we fail in, and just start looking at Jesus more. The more we look at Jesus the more like him we become...and that's what leads to true transformation. That's the way we grow.