priority??

Sometimes i just wonder how does ppl priorise stuff? Is it because of level of interest? is it just because to meet deadlines? Or is it just because u feel like it? Sometimes it's frightening to see how different ppl perceived different stuff and the different actions that comes along with it. Take for instance, what if your frenz stood u up and he didnt even apologize, how will you feel? What if ppl juz throw last minute work to u when u have your own stuff to do? Does that mean that u have to sacrifice your own stuff in order to help out your frens when in harsh reality, you are just picking up your friends' pieces only. Or how about having frenz who claim to organise something soon but the fact is this is always at the last of his priority list?