I'm here to tell you that's not enough. It's nice to have positive affirmations. Thinking is believing and having a belief is nice. I would like to suggest there is thinking and just doing!
Earlier this month I had a couple small children to think about, work had a bunch of deliverables and school work piled up. Frequently I found myself myself asking how I could get all the things done and give the amount of attention my loved ones deserve. There was no 'think I can' it became 'I have to.'
I have to rings in my head when I look up a mountain I wish to run up. Can I do it? I have to!
I believe this fine gent said it best:
<<When I kill that guy, you got 30 feet to get to that guard.
Can you do it? **I have to.>>