How to clear journalctl

I couldn't find in google any safe way to clear systemd journal. Do anyone know any safe and reliable way to do so?

Let's say I was experimenting with something and my logs got cluttered with various error messages. Moreover I'm displaying my journal on my desktop by using Conky. I really don't want to see those errors as they remind me an awful day I was fixing this stuff, I want to feel like a fresh man after this horror. I think everyone will agree that this is a valid reason to clear the logs :P .