We all make mistakes and get frustrated with our builds. It's all the stupid things that make it worse, like saving 30 seconds by not getting out the masking tape and covering up the finish near an area you're working on, and then a screwdriver or spanner slips or a blob of solder falls off and sticks to the finish. So even though you learn, there is still that temptation just to get on and do something quickly than do it properly.

And then there are the days when nothing goes right, so its best to acknowledge that and wait for another day.

Just be aware that you are certainly not alone in feeling frustration and angst with your build!