I use this a lot with my clients. They come and say things like I bite my nails, I eat too much junk, or I lose my temper all the time. So I normally give them this presupposition "every behaviour has a positive intention". Then I go on to explain that when people self-harm they can be in such emotional pain and that self-harming can be a release of sorts, (this is by no means the only reason people self-harm).
That said, self-harming is probably one of the worst things you could do to get a release. The intention behind the behaviour though is a solid and good intention. So is there a behaviour you or someone you know does that does not seem to be productive or helpful? If you take this presupposition to be true the behaviour is there for a good reason. Sometimes the reason is well hidden and if you can uncover it there are better behaviours for the intention. After explaining this to the client (and most of the time the client agrees) I ask, "what is the good intention behind the bad behaviour?" Most of the time I get an answer of "I don't know." Even after the client has agreed that there is a good intention behind the bad behaviour sometimes I get, "there is not one." Each answer is addressed separately. The first answer is very rarely the correct answer; it is just what the client thinks or thinks I want to hear. So figure out what the good intention is and find a new behaviour that is better and gives you what you want.
I was once asked about paedophiles and this presupposition. I was asked what the good intention behind it was. I don't know it; it is normally different for everyone. Then I was asked about if the intention is good should we forgive them? To this I replied "we all have choice, and choosing to do nothing is still a choice the same as choosing to believe there are no other options."