My husband Jon was once in a conversation with a close friend who was struggling with the disappointment of how his life wasn't turning out the way he'd expect, specifically in regard to purpose and fulfillment. Jon's response was brilliant: he said, yes, it is hard to come to that late 20s/early 30s realization that we hadn't achieved more by now -and it's fine to allow yourself to grieve that loss for a bit- but that actually the only thing wrong was our unrealistic expectations in the first place.
But don't dwell on it for too long at the risk of just becoming a cranky douche. Instead, learn to embrace a life of "fabulous mediocrity." (Jon's exact words) Do the work you need to do to survive with a decent attitude and the rest of the time do your best to tap into whatever makes you happy.
I'll add this point: damned if our well-meaning parents aren't somewhat to blame because of their ultimately deceitful "encouragement" telling us "you can be anything you want." Which is why I tell Coen to go ahead and dream big, but don't get too caught up on the end results. Enjoy the ride!
http://www.newrepublic.com/article/121915/dont-search-purpose-you-will-fail