You set your price and put the bike up for sale. If you get it, terrific. If you get it very quickly, then maybe you under-priced it a bit. However that's what you wanted, so revel in having gotten it.

I've never understood getting bad feelings for what the new owner decides to sell it for. If you just realized you undersold yourself (see sentence #2 above), live and learn. And you still made a profit by your original figuring, I should think.

I certainly took less than what I could have gotten in the early days on some of my sales. Its all part of education.

Bottom line: No bike ever got sold unless I was at least good (if not outright happy) with the price offered.