I smoked for almost 8 years and quit about 10 months ago while deployed to Iraq. I kept saying, "I'll quit after PCSing - after new years - after I get married - and on and on." Eventually it just came down to, "Do you want to be healthy and live a long life?" If you do, quit...NOW!!
Combat is more stressful than the LSAT - don't let yourself use that as an excuse.
.....also, to echo the sentiments of others on this thread - massive amounts of exercise and the gum helped for me a lot. I almost slipped up a couple of times but started a strategy where any inkling of wanting to smoke came up I would immediately pop a 2 MG piece of gum. I didnt even let myself consider smoking and towards the end - 2MG will feel like so much nicotine that you will only chew it for about 5 minutes and spit it out.