Moodswings

I've recently started journaling to keep track of how I'm feeling. And I've noticed that I have a tendency for violent mood-swings within a couple of hours. For example, today I was feeling okay (okay, not good) until around noon. In the afternoon, I was in a good mood, to a point that I would almost call hyper: laughing for close to no reason, a ton of energy, and working on creative projects. I even did a light work out. Then, in the evening while I was getting ready to go to sleep, my mood changed again. all the usual insecurities and hopelessness came back up and I kind of spiralled from there.

It got me thinking, and a bit worried. I've noticed these kind of moodswings before, but I'm not sure to which degree they're normal. Of course a person experiences numerous emotions throughout the day, but I don't think I should be going from hyped to depressed like that without any real reason.

Have you experienced anything like this? Any advice on how to cope?