Callouses happen when you work hard. You can get them anywhere where tough skin is required, but what about business callouses?
How toughened is your skin to those bad days? Can you cope? Do you press on with the knowledge that the end result will be good?
I like to think I'm getting my business callouses started. I press ahead when times are super busy or super tough. When the hours are long I remember that hard work will get me ahead. I try to rest easy knowing that I can always BE better. It's not easy and occasionally you have to exfoliate those bad days down and remember what it was like when you first had an inkling to start a business.
It's a balance.