As a beta tester it was a very nice gesture, to receive that letter with the comment "Prove us wrong!" hand written as a P.S. to the form letter. That letter hangs in a frame and every day I use it to remind myself that the only person that needs to believe in me, is me.
Today, many years later, I thank my lucky stars for that rejection. I went it alone, no co-founders, no frigging investor BS, and did not take a dime from anyone.
This year the 17 employees of MY privately held company drove our sales to 61 million dollars in online transactions.
The satisfaction that comes with proving investors wrong can't be bought, only earned.
Those that can, DO. Those that can't, find an investor.