Saying 'No' is became is very difficulty

I am the kind of person that I should say 'yes' to the everybody's proposal though it gives me trouble. Despite many efforts this habit doesn't leave me. I am facing so many troubles with this habit. Can anybody gives me an advice 'How to overcome this problem?'

Balance what favor is their asking. You should try to see things if it's worth it to say yes. Anyway, it's not that bad to say no. Just let them know and try to make them understand why you say no with them. ^^

I also had that similar problem before. I was saying yes to my friends always to please them even though I dont feel like it. But one day I told myself this has to stop because it caused me problems already. I think you really should feel that you that the authority when you say no. If you dont feel proposal, dont be oblige to say yes. Im sure they will understand if you explain it.