Motivation

I am one who tends to get so focused and motivated while working, that I have a hard time stopping or even slowing down. I just keep pushing through til the jobs done. I do know that I am not supposed to lift anything but while working I just forget about my disabilities. It can't be that good for my body, I mean it has to only be hurting me more. It's like I always have something to prove even though I don't have to. I am very work orientated and at times it does scare me in not being able to slow down and push past my own limits. I never even take the doctors advice. I don't know how to handle this and it is natural for me to do this!