Sabotage means damaging or destroying someone's chances for success. When you do it to yourself it's called self-sabotage. The keywords here are chances for success.
In military or industrial sabotage it is usually deliberate and carefully planned and executed with one aim only - to block the competitors' activities which would give them some sort of advantage.
In psychology self-sabotage usually refers to certain behaviours that stop individuals from achieving their goals. It's not intentional. As a matter of fact, in most cases it can be subconscious, but still rather active and persistent.
Lots of people are familiar with those moments when they give up on their diets because they think 'this biscuit/sweet/ice cream is just a little treat' and 'simply won't make a difference' because 'it's only once in a while' or 'it is the very last one'...
Self-sabotage can be very hard to recognise because sometimes it can be just a tiny inner voice that keeps telling you things like: 'what's the point?', 'others do that and they are fine', 'it's impossible/too difficult to do that', 'I can't because..', 'I am too old', 'I was born like this' and so on. This negative self-talk effectively shuts down even the slightest possibility of taking any further action which will leave the person feeling truly powerless and helpless. It's like catch 22.
So, the first step to success would be to deal with these blocks and to learn how to nip any self-sabotaging attempts and thoughts in the bud.