I know that's my weakness

Please.

Please don't ask me if I'm available certain time in the coming future before you tell me what you'd like to spare my time for.

If you'd like to ask me out or for my favour, just say so so that I can always come up with some canned excuses like I'm busy with this and that if I don't want to go though I'm not very skillful at delivering them convincingly.

I'm handicapped in responding the question "Are you free this and that?" properly (especially it's from my colleagues). I will automatically blurt out the truth while I should have tactically hold myself back and asked why instead of giving an answer right away.

ok, I could have said I don't wanna substitute you for your own work and I prefer enjoying my own time even though I have no concrete plans for it. That it's my own time after all and being available for myself doesn't mean being available for you. Or I could have simply said I dun wanna do it or I'm not interested.

BUT. I don't want to be mean to the others, that's why I'm mean to myself -- both of which I don't like. Typical of me--try to be good but sometimes hate to be so.

Siiiiiiigh. I fell in the same trap again and again and I hate myself being so easy to be trapped that if I were not myself I would trap myself in the same way.

Why can't I learn to say no in a socially stylish way instead of grumbling every time I'm asked (in my translation: forced) to do something I don't want?