Gave up alcohol this year, again. I enjoy craft beers and some homebrewed cider and mead, but am hypervigilent coming from a family with some alcoholism. I prove to myself I don't need this, and usually keep it up for a while after lent, then the habit (and calories) creep back in. I also try to do something positive each lent and this year is "something active every day". So far so good.
... I'm giving up smoking (yeah, yeah, bad dog, bad smoking dog!---so mine is a health AND MMM one).
I gave up smoking when I was >1 pack a day long ago. I tried to cut back/quit before then but never had enough commitment or motivation. I finally did it one year for lent, with the help of good friends. My advice: tell everyone you know that you quit smoking, and if they see you smoking, they should punch you in the face! Tell a few friends/family to ask you once in a while how it's going. I really could not have done this without friends and family. Even if I was alone, knowing others would ask and I didn't want to lie to them kept me honest. If there is a quit smoking gauntlet thread, join it! For me the first week was irritating, the second and third weeks extremely difficult, and somewhere in the fourth week I became disgusted by cigarettes. Never went back.
It is very bad-ass to be in control of your life, rather than being beholden to some chemical (nicotine, alcohol, etc.)!