If you were hoping for a 10x improvement but you were only about to deliver something that is slightly better than the current product, don’t beat yourself up too badly. Some days you just can’t hit the home run.
If you are swing for the fences, you’ll probably strike out a lot. Striking out doesn’t feel very good, even if you know that last time you hit a home run.
Keep trying, but some days it won’t work out.