People are bad at predicting what will make us happy, too.

http://pandawhale.com/post/23824/why-cant-we-predict-life-satisfaction-over-the-life-cycle-people-are-bad-at-predicting-what-will-make-us-happy

The only way to discover your strengths is through feedback analysis. Whenever you make a key decision or take a key action, write down what you expect will happen. Nine or 12 months later, compare the actual results with your expectations. I have been practicing this method for 15 to 20 years now, and every time I do it, I am surprised. The feedback analysis showed me, for instance—and to my great surprise—that I have an intuitive understanding of technical people, whether they are engineers or accountants or market researchers. It also showed me that I don’t really resonate with generalists.

Feedback analysis is by no means new. It was invented sometime in the fourteenth century by an otherwise totally obscure German theologian and picked up quite independently, some 150 years later, by John Calvin and Ignatius of Loyola, each of whom incorporated it into the practice of his followers. In fact, the steadfast focus on performance and results that this habit produces explains why the institutions these two men founded, the Calvinist church and the Jesuit order, came to dominate Europe within 30 years.

Practiced consistently, this simple method will show you within a fairly short period of time, maybe two or three years, where your strengths lie—and this is the most important thing to know. The method will show you what you are doing or failing to do that deprives you of the full benefits of your strengths. It will show you where you are not particularly competent. And finally, it will show you where you have no strengths and cannot perform.

Several implications for action follow from feedback analysis. First and foremost, concentrate on your strengths. Put yourself where your strengths can produce results.

Second, work on improving your strengths. Analysis will rapidly show where you need to improve skills or acquire new ones. It will also show the gaps in your knowledge—and those can usually be filled. Mathematicians are born, but everyone can learn trigonometry.

Feedback loops are powerful when you're receiving feedback from others, too.

http://www.forbes.com/sites/danschawbel/2014/03/05/douglas-stone-the-importance-of-feedback-in-business-communications/