Depression can strike anyone at anytime. Nothing quite ruins success like the brain fog of hindered cognitive function. Memory is practically non-existent, and decision-making doesn't come easy.

Simple tasks become increasingly harder and mistakes get made - which causes the motivation to slip and production to go down. That decrease in productivity causes you to miss deadlines, and then you just fall behind.

When you fall behind it's hard to stop and look at the huge pile of shit in front of you. What do you do then? Do you keep going, or do you throw in the towel?

If you keep going you could fail, worsening your depression. You stop. You regret missing your possible one chance. Then resentment and anger fester and grow.

You're in an emotionally compromised position. The question you should ask yourself isn't whether I should go forward or quit. The question you should ask is, "I'm emotionally capable of make this decision on my own?"

You might just have to be completely honest with someone and then talk it out. Although if you catch it early, treat it early.