Become emotionally detached from your great idea. Start empathising instead with your customer. See the wood; it’s made up of the trees! This, in some ways, is a Buddhist philosophy in itself (further reading here).
Your startup is not your product, your startup is your business model.
Your business model must be repeatable, scalable, revenue generating!
To generate revenue you must have customers…
And guess what. To get customers, you have to make decisions that you disagree with on an emotional level.