Well pertaing to the site you are writing for, self sabotage is the main reason people fail at dieting. we constantly tell ourselves no to what we are accustomed to (concerning bad foods and exercise) and therefore we want more of what's bad and nothing to do with what's good for us. By doing this we first create a recipe fot unnecessary conflict (internal conflict) and secondly sabotage any chance of success.
Now on the other hand personally I sabotage myself on a consistent basis, just this weekend I did something that my almost could not forgive for. I won't go into details but lets just say I had misspoken to someone that I had no right to be speaking with in the first place, even though my intentions were good it was wrong of me to do. It is a bad habit that has caused me a great deal of loss in my life. What makes it worse is that I know I am doing it yet do nothing to stop it at times. No one likes to be told no, for most of us it makes us want whatever it is or to do whatever that much more. The only way to overcome it is to learn through self discovery how to recognise and deal wih it in an appropriate manner, ultimately to practice self discipline.
I hope this helps a little bit and good luck.