Failure is the default outcome for most ideas. Thus constant failure is the environment in which entrepreneurs must survive.
But trying and failing for years on end will wear on even the best entrepreneurs.
If you have tried starting a company and failed even once, you know how brutal it is.
You can Google "founder mental health" to see all of the data and personal stories. Some of them are heart breaking.
The reality is it's much easier said than felt.
Take care of yourself founders. There are lots of us out here rooting for you.