I need to stop being a people pleaser

I have always been a "yes man".  I always go along with other people to avoid being seen as lazy or not interested.  Even if I can't keep those promises for whatever reason and that leads to people being disappointed.

I always struggle to say no, or that an activity or place is difficult for me to get to or if I'm not well enough to stick it out to the end.

I should say that the people I'm talking about are the job centre, social workers, volunteering organisations, etc.  Often thanks to my sometimes overbearing parent I'm made to feel like I am in debt to these people.