You can basically change everything in a startup but the market.
We hear again and again from founders, that they wish they had waited to start a startup until they came up with an idea they really loved.
In general, it's best if you're building something that you yourself need.
You have to save the vision speeches for when the company is winning. When you're not winning, you just have to get momentum back.
At the beginning, you should only hire when you have a desperate need to.
... and you can only have 2 or 3 things everyday, because everything else will just come at you; you know fires in a day.