Isn't it obvious? I mean, I'm not sure why you're asking, it seems self-explanatory...but, I'll try to explain.
If you work on things you feel are important, you'll be more energized and motivated, where as if you work on things you don't really care about, you'll constantly have to be forcing yourself to slave away at the drudgery. And, of course, accomplishing things you care about makes you fulfilled and satisfied, your life has purpose and meaning, and your work probably does the rest of the world a lot more good, too, because if you're passionate about something, there's probably a good reason, whereas a lot of menial jobs are more or less unnecessary in the grand scheme of things.
And working with people who think like you is important because it increases harmony and the chances of you being able to realize your goals, through cooperation with like-minded individuals--people who are aligned with your goals, and also people who think like you will understand you better and vice versa which is great for communication and efficiency.