I don't have to believe a process will work for a process to work.
I just have to do the process for it to work.
If I did not believe that lifting weights would build muscle, but I lifted them anyway, I would eventually build muscle.
(Sure, sure, believing in a process can help me be willing to do it, or help me focus my energies so that I get the maximum result from it, but I can get a result from a process solely through action; belief is not required.)
That's been an important thing for me to learn.