Take heed in that thinking is not being assured.  Know something is better than thinking it.  I may think I stand, based primarily on a belief or conceit,  I know I stand based on the foundation that is tried tested and true.  I know something when belief itself is inconsequential and irrelevant to proof.  I know and the knowing is proved.  I think and therefore I need or require proof of it being so.  Something either is or isn't.  Nothing wrong with being sure, something wrong with being affirming that I am sure when I only think I am.  When I know I am then I will stand and not fall.

There is a passage of scripture  which attests in part "...who maketh my feet like hinds feet, able to stand on my high places."  Probably in one of the 'Prophets' as they were more than men/women of faith, they knew.