How do you handle work when your personal life interferes?

Due to multiple problems going on in my personal life right now, I am feeling very depressed and having trouble staying focused/motivated at work. I am afraid my performance will suffer. I feel like I can’t handle work on top of everything else that is going on right now.

I am working on scheduling a counseling appointment right now but I don’t know how long it will take before I get an appointment, and then how long before it begins to benefit me, and I work in a very fast-paced and demanding environment.

Do I talk to my boss or just keep trying my best and hope that nobody notices a decrease in my performance?