With the introduction of competitive audits, one thing became clear: It is almost impossible for one auditor to find everything.
Since the start of my auditing journey, i always attempted to find every single issue in all contracts that I have audited and so far I hope I did a pretty good job, as I usually find most issues that my co-auditors spot.
Of course it naturally happens that you miss an issue, but what then?
The way to move forward is reflect on WHY you missed the bug. There could be many scenarios:
a) Insufficient attention to this part of the codebase -> be more thorough next time
b) Lack of creativity -> try to illustrate the business logic of the specific function/contract and thing of "what could go wrong"
c) Insufficient understanding -> simply keep on grinding