I remember praying and saying "Lord, why is that I can please you in everything else, but I keep fearing that I'm going to fall/sin in this one particular aspect of my life?" (First of all saints if we fear falling, it means that we have an expectation that we're going to) and while praying I heard when the Lord said "If you fear falling it's because you have denied the power of Grace" Immediately it's like my eyes were opened for the first time to the scripture in Jude 1:24 - Now unto him that is able to keep you from falling, and to present you faultless before the presence of his glory with exceeding joy.
At salvation God gave us Himself, because he ALONE can please Himself. The Bible says that flesh cannot please God. So the moment we start depending on our willpower, we cease to walk after the Spirit and instead walk after the flesh. What we are basically doing at that time is depending on the flesh to produce righteousness and Godly emotions, which is impossible because our own righteousness are as filthy rags before him.
John 6:29 Jesus answered and said unto them, This is the work of God, that ye believe on him whom he hath sent. ALL we have to do is just TRUST and BELIEVE that he can keep you from falling because it's his life that's going to save us and not our own willpower. That's why God told us to REST.
Hebrews 4:3 For we which have believed do enter into rest.