Why cant I say NO

I have a BIG problem in my hands and it can be said in just one word 'NO'. I dont know why this word dose not come out from my mouth and due to this I have put myself in many unwanted sititution which I would have avoided easiely if I would have said NO.

I think that there is some part in me which always want's people to say good thing about me, may be this is one reason why I cannot deny any one even if it means that I may get in to trouble.

May be this being the reason I am more often then not left anlone to face the music, where as others are enjoying the sun I am covering up for them and many a times when my friends get in to my position they give some reason for why they could not cover my a** .

I know that you may feel that I have a wrong group of people who I call friends, but this is not the case I have been friends with lot of them for the past many years and some of them are really nice to me, thry some times understand the problem which I face and try their best to solve it or even if they could not help me they just stand by me till I get out of the mess which more often then not is created by me.

I have heard that once if you say the magic word life becomes easy and more colurful but I am afraid of the fact that I may hurt them. Most of them relax just just by knowing that it is I who have to do the job and everyone is confident that the work will be done before the deadline.

I just fail to understand that why do people take me for granted as if I dont think or that I am a kind of machine which they can use when ever the need arises and forget when its their time to help me.

I also take a share of my responsiblities as I am not able to express my emotions to every one I dont know whether any one understand me or not and if this continue I dont think I will be living the life which I want to live and I am truly afraid of this.

I am a person who have lot of thing inside me but thoses emotions stay with me, this is the worst part of my nature that I leave it to people to imagine what kind of person I am instead of showing my true self. The best or the worst part being that most of them say that I am a good person I dont know wherther it is true or the persons around me say nice things just to keep me with them as they have to use me later.