How to trust your conviction that you can then follow vehemently.
1. Success of someone else with similar beliefs.
2. Trusting your own past success.
Believing convictions others have championed leads to inflexibility to correct them en-route. The game changes when circumstances change. A different time is a different circumstance. A different person is a different circumstance.
You have already established that since the other individual succeeded with this, its going to work for sure. There is no sense of vulnerability.
In the beginner’s mind there are many possibilities, in the expert’s mind there are few.
Strong convictions loosely held.