I've always wondered whether we should pursue what we
want or what we
need. For a long time I had no definite answer, but then I realized pursuing what we
need is more important.
In fact, this comes in part from this understanding that there's no good or bad, rather there are things that make us happy and things that make us sad. These are not always consistent though. For example, we might get sad at something which later we find out was - based on rational and logical considerations - actually a good thing, or become happy at something which is in fact a bad thing.
Our "wants" promise us "happiness", but the joy we get from that is most likely short-term. On the other hand, pursuing our "needs" brings about "good" things in our lives, the joy of which is more long-term. And while getting what we need doesn't necessarily makes us happy, not getting it does in fact make us sad.
Two problems exist though: (1) while we think we know what we want, we might in fact have no clue as to what we really want, thus always follow wrong leads; (2) we can only know what we need after we have achieved it. It takes a lot of self-knowledge to really figure out "where we are supposed to be", "what we are supposed to do", and "when". The answers to these questions tell us what we actually "need".
Example: a person with talents in music but interested in math (in which he/she is only mediocre) is better off pursuing music as that is what he/she needs to do. What he/she wants to do is however, math. You tell me: wouldn't pursuing a dead-end job in math bring about an interminable series of sadness where the person realizes he/she can never be among the top math geniuses?