It takes a lot to pull off a performance. Hours of practice. Traveling to the gig. Lugging heavy and awkward gear around. Setting up, getting the sound dialed in. And that's all BEFORE the performance even starts.
There's always doubt in the waiting. Waiting for that friend to text you back. Waiting for that project you've slaved over to finally wrap up. Waiting to find a significant other. Waiting for those test results to come in.