In addition to what has been offered thus far, there's an additional angle I'd like to point out.

No one can really sabotage you, except yourself. We do sabotage ourselves by taking the bait, when the opportunity arise, and sometime even create the opportunity.

Why would one try to sabotage their efforts? Because we get something out of it, without knowing it. If you're working hard on losing weight, endulgance in no-no's may give you a break from the effort involved in sticking to it. After the fact, "he/she tempted me" also offers an excuse to why I didn't stick to it and stand my ground, thus releiving me from facing the fact that I didn't stick to it.

The above can go on in cycle, until it's broken by recognizing the real reason why we allow ourselves to sabotage our efforts, and dealing with the underlying issues to break this cycle.

Wa'il