While doing anything serious, or anything at all, Lincoln’s advice is spot on. He once (in extremely trying circumstances) said:
If I were to try to read, much less answer, all the attacks made on me, this shop might as well be closed for any other business. I do the very best I know how – the very best I can; and I mean to keep doing so until the end. If the end brings me out all right, what’s said against me won’t amount to anything. If the end brings me out wrong, ten angels swearing I was right would make no difference.
These are really powerful words. They resonate with you every time you are at the helm and you are disappointed. Perhaps not so surprisingly, like other walks of life, these words apply to entrepreneurship. While doing the things you do, there are challenging moments and keeping such a “being with the end in the mind” approach helps.