Pretend it isn't personal, pretend it belongs to someone else for a moment so you can look at your work objectively.
If a fighter loses a fight, he starts training for the next one. That is what you need to do, shake it off, and start training for the next one.
Just because you thought something was a good idea doesn't it mean it was a good idea. If a product isn't selling, tweak, test it, but in the end, if it is not working, stop selling it and find another. The important part is the model, how it works, not what product you are pushing through it.
If the product doesn't work, it doesn't mean you failed, in fact you have done something great, you tried something most people just talk about, or wish for, but never actually get off their couches to go do.
You did it, you got started, took the leap/
Selling a product that didn't work just means you need to try something different, you learned something from that product that you can use on the next product, and on the next, You learned what doesn't work, you learned new skills.
The only way selling a product that doesn't sell hurts you is if you are too stubborn to learn from it and move on.
If it doesn't sell, pick something else.