Getting out of a rut.
If you've ever been in a rut, you know the feeling of helplessness. It seems impossible that you would ever get out of it. But you do, every single time.
You have to remember that it's a negative feedback loop, and the longer it goes on, the harder it becomes to break it. You lose confidence day by day and continue with your negative self-talk, pushing back against anything positive said by others.
It is simple to get out of this, but you must follow the necessary steps. You need to treat this period like you are ill. Fix your sleep schedule, eat nutritious meals, exercise (in any form), talk with friends, and get enough sunlight. These may seem like chores when you are down, but just persist long enough, and it will go away like a bad flu.
I can write essays on all the mechanisms on how it'll help but it is not necessary. You just have to do it. You'll feel better and you already know it deep down.