Self Defeating or Self Destructive?

I have spent most of my life dealing with long term clinical depression, though I've only sought medical treatment on 2 occasions. On my last visit with my Dr. he encouraged me to either go to therapy, seek out a support group, or find some way to get my issues out in the open. So this will be my way.

There are often times where I question the vicious circle of the things that I do. I've never really put too much thought into these things until recently. I'm not talking about anything horrible or illegal, just things that I know better than to do. Smoking, eating things I shouldn't (when I'm on medication for high cholesterol, and high blood pressure, as well as having a great deal of heart disease in my family), not exercising anywhere near as much as I should. Just in general not taking care of myself. Sure I can do anything for a while, pull myself together, take better care of myself, that goes on anywhere from a few weeks to a few months, but for some reason I just don't seem to ever make it stick for good. Now here I sit, stuck with this question. Are the things that I do, that I know I shouldn't simply self defeating, because I've become lazy, even stagnant with the way that I've lived up until now. Or are my actions subliminally self destructive because I don't really like the person I feel I am at times. I guess it's something to spend the next few days contemplating.