I’ve been saying this for years, but failure is the price of success. The corrollary, which Churchill hinted at in his “success is failing and continuing with undiminished enthusiasm”, is that failure IS success, when viewed properly. Why does failure hurt? Because we attached ourselves to a given outcome. We created a tender spot in our emotional body over which we had no direct control.
The task, as I see it, is to radiate out, such that nothing in the external world can hurt, but such that you support everyone out there. This is, of course, much easier said than done (like virtually everything else). Towards that end, frequent failure is an immeasurable boon, since it prevents self importance, and it teaches you not to be too attached to things beyond your direct control (although obviously things like effort, preparation, and attention affect the outcome; this is no excuse for sloppiness or laziness). If you truly can fail, and not be affected in the slightest, then go again, then go again, then go again, the entirety of your life, at some point you will pass beyond really caring about any difference between success and failure, and focus only on the pleasures of the process.
And once you can do that, you will be reliably happy.