Why do we pause to gear ourselves up before a big jump, a heavy lift, or a fast sprint? What exactly do we expect our brain to contribute to the task at hand? The brain is simply going to acknowledge how HARD and CHALLENGING and INTENSE the next movement is going to be. If you wait for your brain to be excited it about it, you are probably going to wait forever. Your brain is very smart and knows that whatever horrible exercise you are about it to do is not going to be comfortable.
Move first. Let your body lead. You don't need to "get there mentally." Let your mind follow your body, for once. If you take that step RIGHT AWAY, without analyzing it, you will see just how powerful movement is. That first step will define your mindset. Rather than waiting for your brain to believe that you are strong and powerful and resilient, your brain will see a concrete demonstration of that power and then work to support your training.
We can waste our lives waiting for the right moment. But sometimes you need to move and the moment creates itself. When I was in college, I read a quote in a class called "The Summons To Adventure." Here's the quote: "We live in the mind." And many of us do. We spend our lives fantasizing about experience we will never have with people we never have the courage to know. We are hung up on fictional TV characters who don't even exist. We ping pong in our skulls analyzing and imagining and second guessing. And thinking is incredible. But would you rather dream about a mountain or climb one with your own two feet? The irony of "The Summons to Adventure" is that we don't need a summons. We just need to start moving.
Move first. Your mind won't be ready, but your body is. It's not an adventure until you are in motion. So move it.