Just as you said that buying at 15k is stupid, in future selling at 3500 could be a great deal. What is it goes to 1500.? That's a 100 gain if I buy back.
The point is that we're already down 90% and the probability of going down further decreases exponentially as we go down. You're just falling victim to the gambler's fallacy right now.
Edit: What if it goes down to $1? It was $1 before, I could sell one Bitcoin and make 3500 Bitcoins! (fat chance)
Edit2: Invest some money in a book on investing and balancing portfolios. Read it, study it. Everything you post cements the fact that you're just gambling based on emotions. Emotions that traders use to take your money and make profits.