I don’t think we can really grasp the concept of never failing. Ever. God’s perfect understanding of everything and everyone is so much bigger than our comprehension, and yet we still try. Why do we get upset when people (or ourselves) fail though? That is our humanity - and we have to be careful not to put too many expectations on people and put them in God instead. He is the faithful One, He is merciful and He is with us!
“The Lord is righteous in her midst, He will do no unrighteousness. Every morning He brings His justice to light; He never fails, But the unjust knows no shame.” Zephaniah 3:5