Take care of your body and your mental health.
Try to turn any feelings of inadequacy or imposter syndrome into energy to push yourself forward and increase your skills and knowledge. We've all been there... multiple times.
Learn to code fearlessly: Are you being asked to run queries on a production box? Ask if you can get a user with read-only permissions. Change crusty old code? Maybe put a quick test harness around it.
If you're stuck when debugging a problem, think about all the assumptions you're making, and then test each one of them, no matter how obvious.
Understand that code is often ugly and weird for a reason other than incompetence. Code quality tends to be a function of time, requirements, experience, and skill.
When I manage to get a team to create a code base with good tests it turns out that it's easy to change and resilient in the face of sudden requests for features.
A poor test infrastructure doesn't do this, building a good infrastructure is a skilled task. But worth it!