I've got two similar expressions for you. They both describe the nature of human imperfection this way: no matter how good you are at something, you still have flaws.
even Homer nods (the legendary Greek writer Homer is considered one of the most important and influential authors in the history of European literature):
Not even the most vigilant and expert are immune to error.
Although originally a Japanese expression, the phrase even monkeys fall from trees (monkeys are supposed to be experts when it comes to tree climbing) seems to have become very popular in the English-speaking world:
It suggests that even the most skilled, can make a mistake in something they should be a master of. Or, to put it simply, "Anyone can make a mistake."