What makes something worthwhile?

I mean, really, everything is worthwhile depending on the way you look at it.  One can always gain new experiences even from doing a similarly redundant thing.  Even working on an assembly line- doing the same action over and over again- gives you knowledge of that particular product you are making, or it trains your body and mind to perform a specific action.  The question quickly becomes, "What could I be doing that is MORE worthwhile to me right now?"  I know it sounds selfish and maybe capitalistic, but you quickly run out of energy if you're doing something just for acquiring any type of experience or knowledge, or if you're doing it for somebody else.  Granted, if you're doing charity work, that is for somebody else, but you are also getting something wonderful out of the work. 

You have to choose, if what you're doing isn't giving you the experience, skills, or knowledge you really need or want, to switch to something that does give you these things.