Heart is not all there is to it. There are those who seem willing that also will not take instruction -- that to me is not "willing" at all.
I do believe that there is far too much criticism in the aisles from people who can't do any better, and who cripple those trying out of the goodness of their heart and in a voluntary capacity to present music to the congregation by chopping the music dept budget. (no we are not paid, just for music supplies and such). Or they will complain about the 'sound balance' when they refused to put in an adequate sound system when budgeting for building expenses. Those people's criticisms I just let roll off.
I disagree with this also. If you are in it for perfection you had better wait to sing until you get to heaven I guess. God is FAR more concerned with the relationships we have with each other and him than how perfect our presentation is.
But I do think it is a thrill to sing challenging music with an excellent group. We sang Wuorinen's Genesis with the Minnesota Orchestra - as well as Beethoven's "Calm Sea and Prosperous Voyage" -- (which wasn't nearly as challenging but fun all the same) -- under Edo De Vaart when I lived there back in 1991-92. In smaller towns we did Bach's St Matthew Passion wherein I had the "where is my jesus gone" solo - and lost myself in the music so much that everything vanished but the music, in my mind. And in one performance I had to stop and get ahold of myself during a choral part (Right after the disciples ask "is it I?" -- the choral part "t'is I who should be sharing..." nails me just about every time!) . A few others did the same, and the director, although he warned us earlier to detach ourselves emotionally so that didn't happen, was very understanding about it... because he was a pastor and loved the Lord, I am convinced. He knew perfection was not the main concern here, even though excellence is always something to strive for. We also had solos sung by not so nice voices as well, which he helped compensate for (gently) by having them done as a small group with a few stronger voices to support their wanting sense of pitch - and the audio balance on the recording is really lame.
There have been times I choked up singing in church too, especially when I am really struggling with something of course - and then beat myself up about it because it screwed up the song, only to find out that everyone was moved by my emotion.
I grew up in a tiny church where my best friend and fishing buddy was a retired old man who couldn't carry a tune in a bucket, and yet he was not bashful of singing heartily during the service or throughout the day wherever he was. And we all loved it. At the same church was a little old lady who'd sung under my dad and who couldn't play piano worth a lick but would do so in a pinch when no one else was available. (she knew she couldn't play well and that wasn't my problem with her...) She would also not hesitate to offer gossipy criticisms just loud enough for us to hear, of my or my mom's choice of song, me when I was a teenager just getting used to the idea of really *singing* solos in front of church.
And then there are my siblings who are professional musicians - one plays French Horn extraordinarily well, but doesn't know the Lord, as far as I know...
And one who is an excellent flautist who studied under Rampal for a time. She's kind of flaky and also doesn't know the Lord and is actually kind of destructive as far as the family goes.
So basically I find all I can do is follow the Lord's leading as best I can, and try not to take criticism too seriously, whether it comes from pros or from "armchair quarterback" type musicians. I'd rather go about with the "poor lot" that Christ went about with. They are much more 'real.'