Time is the coin of your life. It is the only coin you have, and only you can determine how it will be spent. Be careful lest you let other people spend it for you.
-- Carl Sandburg
Yes. I've sometimes been astounded at the willingness of some people to have others waste their time. They won't turn them away, just out of... I guess, politeness. Granted, it is not the easiest thing in the world to just say No, but at the price of having your life wasting away underneath you?
I had a spiritual tutor back in the eighties. He told me a price per hour before we started. He was really helpful, and then after I held out a hand with the money. He didn't take them immediately, like he really didn't want them. Then he said: "do you know why I say I charge money for it? It's because otherwise some people are just time-sinks for me."
Happiness is essentially a state of going somewhere, wholeheartedly, one-directionally, without regret or reservation.
-- William H. Sheldon
I also believe this is true. In fact, for many intelligent people, their biggest problem is that they are not sure what their purpose is! (Books about finding your "true purpose" are selling very well.)
I've come to believe it doesn't matter, actually. Our true purpose is probably too big for a human mind to understand, so whatever you choose in your human life is just that, a choice. Just do whatever you're good at, and do it with love and do it well.