Why do people persist to do things that kill them?

This is a post that I, and the human race could probably write and expand on for some time into the future. Anyone who keeps up with my blog should know, when I write here, I try to keep it brief. I like to give you some reasons I (and others) believe it to be a certain way. This post is no exception, so here are a few reasons people persist in things they say they know are bad.

One essay on http://www.helium.com claims the reasons are:

1.  It's a habit. Anything can be habitual under the right conditions, if it is a habit, it is hard to break. You probably have heard the saying, "old habits die hard". 
2.  extreme circumstances
3.  ignorance
4. poor training (lack of discipline)
5. inexperience
6.   lack of impulse

Yes, there is some truth to everyone of those reasons. I would say that sometimes it is they don't know how to change (ignorance), but very often, even this reason could be overcame if people learned to do what I am about to tell you next.

People need to do new things, occasionally including things they really have no inclination to do. There is a good saying for this, too. If you always do what you've done, you will always get what you've got. I have a quote of my own,

"growth is usually on the other side of whatever you don't want to do." -David Coeyman

Please, for the love of the lord, use good sense here. This is true though, what needs to be done tends to not be easy? Why? Not because life ain't fair, but because if you didn't want to do something and you knew what could be done to change it, and it was easy, you would have did it already. People tend to keep doing things that kill them because it is easier to deal with the stress and disappointment of persisting in this (what you know and are use to), than to persist in that uphill battle that a new habit building can be. Life is painful, so it's not pick your poison, it's pick your pain.