The work and career of a researcher is never smooth, and is typically
littered with rejections, wrong turns, and (in retrospect) not very smart ideas.
I strongly suspect that this is true also for other activities and careers, however I lack direct experience of them, and would not like to unfairly tarnish them with the same brush!
Inspired by the example of others, I try to summarise various unsuccessful job applications and funding requests. The oft-repeated mantra that we "learn from our failures" is probably true, but they can none the less be frustrating and disheartening.
The message is that you need not give up ideas of a research career after a few rejection letters: it's quite normal!
IF you are able and willing to put up with years of wandering around, wondering what will happen in the long-term, you MAY "strike lucky" and find yourself applying for the right research job, in the right place, at the right time.