In baseball they have this statistic called VORP which signifies how much better a given player is than a fictitious player that the team could pick up and stick at his position. Basically it is a proxy for that player's marginal utility. It's a ruthless statistic, because players are given no credit for making it to the big leagues in the first place.
I've been thinking about VORP and trying to generalize it to other walks of life. It seems that for any competitive position it is instrumentally worthless to only measure what you yourself will accomplish. Instead, you must consider how much better or worse you will be the average person who would replace you if never enter the field, gain acceptance into the prestigious university, receive the NIH research grant, secure some of the limited venture capital funding, or whatever.
I've come to the conclusion that unless you can show by some objective standard that you've identified a niche where you can achieve very high VORP, you might as well just sit back and enjoy the ride. But if think you can accomplish something that nobody else would or could do otherwise, then rejoice, because your VORP will be infinite.