How did posses work?

Is joining one a fun and exciting prospect or is it more like jury duty? Do I hate the idea of riding all day in the hot sun squinting at the horizon and hoping I don't get shot or hurt my horse or is like a cool pursuit? Am I motivated by anger like a lynch mob or am I just solemnly doing my manly duty to keep the community safe?

Anyways it's my daughter's birthday today, can I get off with a "Maybe next time fellas, good luck?" My friend has plans on Thursday he needs to be back for, so he can only join for a couple days, is that cool? The sheriff seems incredibly dumb, it's hot, my little brother is annoying the hell out of me, he didn't bring enough food and is eating all of mine, the excitement is wearing off, had to close my store and I really need the money, who's going to wrangle my cows, I really have to finish planting.

Is there anything stopping any of us from saying "This sucks, I'm headed back"? If my horse gets hurt do I get compensated? If I get killed who watches out for my family?