How much failure is too much?

I have been thinking a lot about failure. Obviously, I have been submitting my work to literary agents and, while I have received kind responses, nobody has taken me on. Let me start by saying that I believe in the idea that failure=not trying. I truly subscribe to the philosophy that you need to work through failure - sometimes a lot of failure - before you find success. But how much failure is too much? Or, maybe put a better way, are we as individuals too biased to see that our dream is completely unrealistic? We all have those friends who have dreams and on the outside we are saying "You should go for it!" and on the inside we are thinking "You are never going to achieve that." Heck, I even think that when my kids tell me their dreams. I support them and would never in a million years tell them they couldn't achieve something...but the practical side of me knows how unlikely some things are. In books and podcasts we hear over and over that the people who make their dreams realities are those who just didn't ever stop. They failed over and over and just kept going. I have to wonder, though. Did everyone who kept trying eventually make it? Or did some people just fail over and over again forever!? The latter seems pretty likely (again, think of those friends...). The other option is that, with enough failure, the dream shifts. It morphs into something else. So, the question I have for myself is: when is it enough? When do I decide to pursue other options and give up on that particular dream. Is it giving up on a dream if you choose another path? I feel like you should definitely give up on a dream when you have given it a good go, but doing so is causing stress or harm to others. For example, if you are chasing a dream, but that means that you aren't able to make money to support your family. Or you are taking so much time away from your spouse or kids to make your dream a reality. The collateral damage seems like the key here. So, if I can chase this dream with no harmful effects to those I love (besides constantly having to listen to me talk about it), is it worth continuing on? Does constant disappointment count? Such that, at some point, I should pull the plug? I am actually pretty good at setting success markers that I have control over and have nothing to do with seeing achievement of the actual end goal. "My success today is simply submitting to an agent!" Theoretically, I could continue this process forever...or until I have queried every literary agent and publisher that exists (whichever comes first). But this means that I can't put my work out there for people to enjoy, and that is truly the end goal for me. Self-publishing seems fun and exciting, so part of me would be totally happy going that route. The other part of me would feel like I gave up. So there's that.