Hi Nathanael Erik,
Try not to despair, although I know it can be tough to attempt to do so.
Remember that your brain is undergoing some chemical changes and that may be what's causing your depressed mood.
Focus on yourself, your recovery and your well-being.
Most concussions resolve and completely heal in the first few weeks to a year. You might just wake up one day and feel completely back to normal!!

Although if you do, please remember to take it easy since your brain might still be vulnerable to relapses and further trauma.
Try to be patient.