I've sold tons of Bitcoin at around $200 and also sold even more ETH at around $5-$10 a coin. I sold because at the time it looked like a fair price and I needed to money to pay for electricity and buy more GPUs.
Yes if I've held till now I would definately get much more for it but you can't predict the future. At the time BTC when it traded around $200 it looked like it would break $200 support and head into the $100 area and maybe even double digits. And ETH at the time of the DAO hack was not looking good either, and it could of went back to $1 ETH a coin.
Sure if I knew what the future would bring I've obviously would of held but I didn't. Same with you selling at $3000. You said you knew it was going to go up but how sure were you? Not very. It could of went to $2000 then $1000 and you wouldn't be able to buy food like you've meantioned.
Thank you @adaseb for this great post. Would have given you a Merit but you don't need it, as you are already a Legendary

No one can predict the Bitcoin movement for a certainty no matter how hard they try. We all can only guess. Even at the current price, no one can say for sure if the price will go up tomorrow, or come back at $3,000. As you and OP said earlier, no better time to sell Bitcoin. Any time is a good time, provided you made some profits and used the proceed wisely.