"If you have faith as a mustard seed... nothing will be impossible for you." (Matthew 17:20)
As a Christian it's easy to initially respond to the Gospel in faith, but as the walk goes on, the new Christian can slip into a pattern of "doing it myself". It's also easy for a Christian to be faithful in the expectation to "earn" something, or perhaps make our relationship with Christ better.
There is nothing we can do to increase our standing in God's eyes! Faith must also be tried and tested, otherwise it's an empty and shallow faith. Better is the Christian who has the faith tested, they emerge stronger in the Lord in the end.
On a personal note - faith is very hard for me! It's so easy to come up with that "backup" plan when I say I'm going to trust in the Lord. "I have faith in you Lord, but I'll come up with this backup plan just in the off chance you don't come through."