Focusing on the positive


What’s the difference between focusing on positive thoughts versus suppressing negative thoughts ?

For example, I’m trying to focus on the positive at work but negative thoughts do come up especially when I have bad days. On the bad days, when someone asks me how my day was I don’t want to bring negative energy/focus into the conversation so I just say it was fine. This seems unhealthy as it seems to be a suppression of negative thoughts and experiences.

How can I focus on the positive in a healthy way?