Good times:
A good presentation, your team is enthusiast about an idea, you just got a blogpost on a popular blog, an exciting companies want to start working with your service, you just gained a customer, ...

Bad times:
A deal you worked on for months just got killed, you feel like you never going to finish a certain feature or service, your service has a major downtime, you get a mail from a complaining customer, you lost a customer,...

These are the ups and downs when you're starting a company, and if you're passionate about the stuff you're building, this can be a real emotional roller coaster. So it's essential to keep everything in perspective. I learned it helps to be an optimist when it's going bad and be a bit of a pessimist when it's going good. Optimism triggers persistence (because you still believe you can overcome the problem) and pessimism triggers realism (which keeps your feet on the ground).

This doesn't mean you shouldn't allow yourself to throw a small party on good news or be a pain in the ass for a day on getting bad news. As long as you remember that the next day: it's business as usual.

image by pattylagera