One in a million
The chances of a high school student eventually becoming first violin for the Boston Philharmonic: one in a million.
The chances of a high school student eventually playing basketball in the NBA? About the same.
In fact, the chances of someone growing up and getting a job precisely like yours, whatever it is, are similarly slim. (Head of development at an ad agency, director of admissions for a great college... you get the idea). Every good gig is a long shot, but in the end, a lot of talented people get good gigs. The odds of being happy and productive and well compensated aren't one in a million at all, because there are many good gigs down the road. The odds are only slim if you pick precisely one job.
Here's the lesson: the ardent or insane pursuit of a particular goal is a good idea if the steps you take along the way also prep you for other outcomes, each almost as good (or better). If pushing through the Dip and bending the market to your will and shipping on time and doing important and scary work are all things you need to develop along the way, then it doesn't really matter so much if you don't make the goal you set out to reach.
On the other hand, if you live a life of privation and spend serious time and money on a dead end path with only one outcome, you've described a path likely to leave you broken and bitter. Does spending your teenage years (and your twenties) in a room practicing the violin teach you anything about being a violin teacher or a concert promoter or some other job associated with music? If your happiness depends on your draft pick or a single audition, that's giving way too much power to someone else.