Do I trust myself?

As I get more in tune with my self talk and focus on my mental skills it raises some questions. I can create all the positive affirmations I want, but, I need to be able to trust myself to stay true to them. I will give you an example, the snowshoe race 10 days ago. I have run a particular section of that race numerous times and I rarely walk the steep pitches. I found that I walked, even if it was only for 10 steps, where I never have before. Now, this may have been because I went out a little too fast, but I was really upset with myself. I knew after the race and somewhat during, that I probably didn't need too, but at the time I managed to convince myself that it was necessary. How do I fix this?

I am wondering, if I didn't affirm (that I would run strong on the hills) enough times to myself and just expected that I would naturally do it. My question is how can I trust that I will do what I have promised myself on race day. What happens when I have this voice saying you need to slow down? I know that I can always push myself harder than my mind tells me, but sometimes the mind wins - I hate that. I believe that I need to start trusting myself, but I am not convinced that I am able to wholeheartedly do this just yet. I can't believe have trust issues with... myself!