Brother Bill stated Faith in Jesus is simple. Faith is simple to begin with, but saving, lasting faith no matter what happens to you?? That my friend is far from simple. Remember Peter as you stated? Remember what Peter did after Jesus was crucified?? Peter thought all was done and went back to his old lifestyle. (John 21:3-7) He felt so back he threw himself into the sea!! lol I do not know of a single person.
Who has not fell back from their faith, including me! But like ALL the disciples who fell away (Matt 26:56) when one does come back, they come back for good!! They come back having now a FULL understanding of what friend they looked to leave behind!! And like me, know that no matter what happens to me know I will never forsake my Jesus ever again!!
We all have doubts. at one point or another in our faith, Jesus has none and states you should not either because Jesus said if you love me you must love and believe the Word, I gave to all my believers!!(Matt 28:20) HOLD fast my friends to this and place your utmost faith in this assurance!! As my Old pastor once stated to us DOUBT and do without BELEVE!!!! and you indeed shall receive!! (Mark 5:36-37) Please notice verse 37!! He allowed NO ONE who would not believe hence why he only took Peter, James and John! AND!!!!! NOW we who do believe!! Blessing always!!