Novice testers can struggle with accepting this concept. They tend to moan a lot, develop a negative attitude and start mumbling nonsense like 'what is the point of writing bugs if they won't fix them'. Understand that as a tester your job is done once the information is reported. Recognise that you cannot be personally held be responsible for decisions about quality that are made by others.
If you do have the misfortune of existing within a forsaken organisation where blaming testers for the existence of bugs is deeply in-grained into the working culture, firstly, you have my deepest sympathy. Secondly, you can always show the powers that be your WNF'ed bug report and politely point out the issue was previously raised (aka the 'I told you so' manoeuvre).
Don't moan, test more.