Despite the popular notion that you must aim for perfection to succeed, I'm going to give you a different view point.
More often than not, it is perfectionist that achieve way less than the "doers". Aiming for perfection is somewhat akin to missing the wood for the trees, in other words, most things do not require ultimate perfection, they require action.
I remember watching an interview with Stevie Wonder in which they asked the mix engineer to solo each instrument of one of his famous songs. When they solo'd his harmonica part, there was a part where he clearly went horrible out of tune. Steve's response was to laugh and say that he messed up, oh well!
I bet that Stevie's songwriting grew with a similar free attitude. Despite his songs sounding perfect to many ears, he probably got that good from writing tons of songs, many bad ones and many good ones, until eventually he found the patterns for creating more good than bad!
Then there are other very successful artists who seem to produce fantastic music followed by lots of average (and sometimes bad) music. This used to confuse me, why would they willingly put out lazy music? I was looking at it from the wrong angle, they weren't willingly putting out lazy music, they were putting LOTS of music out and sometimes they'd hit upon a gem.
The simply act of producing lots and lots of music results (naturally) in an overall improvement and a few gems. It is lucky for them that they were not perfectionists!
I'm not suggesting you forget about practicing or aiming for the highest standard you can, I am merely saying that being a perfectionist is one of the most limiting traits a musician can have and in some cases can be paralyzing.
Singers are the most vulnerable to the paralyzing nature of perfectionism. As a producer I can tell you that it is MORE important that you have a good tone and you sing with confidence that you hit each note perfectly. We can fix the odd pitchy note here and there, but we can NEVER fix a poor vocal tone or a weak (non confident) performance.
Let me go further. When you record with me I will happily listen to you sing horribly out of tune dozens of times if you are trying to get some energy in an adlib for example, because I know that when you get it, it will sound awesome. Contrast that with a singer who refuses to "go for it" in case they accidentally sing out of tune, this is very limiting.
Be free, expressive, non perfectionist in your music. Smile when you sing and don't over analyze too much when you write songs. Your aim is simple, to produce a lot of music, bring joy to others who listen to your art and avoid getting bogged down with details that no one else will notice!
Quincy Jones says that you should do everything to your best ability but he also says that you should not get "paralysis from analysis"!