Keeping a daily journal helps you to gain some distance on your thought patterns and observe the way that they affect you. You may also discover how things like your sleep patterns and biorhythms affect your mood. This can make it easier to find constructive ways to deal with your thoughts and feelings. You might also try doing a page or two of positivity or gratitude exercises.
Getting enough exercise also has a tremendous impact on mood, as much as taking a prescription antidepressant. Even though you might not feel comfortable going to the gym due to coronavirus concerns, you can still take a walk around the block or go to the park. Exercise videos can also be a good way to get moving while staying inside.