It's not really that cruel when the value goes from sub $1k to $6k+. It's all about timing and luck. Bitcoin has made many people wealthy and many more a nice little profit, but with great successes there are also the great losers who bought or sold at the wrong time. For all those that made thousands during the rally there are also those who lost thousands by buying it at the all time high and are now grossly out of pocket, but as with any investment this is something you either need to accept or understand the risks of because there's always going to be winners and losers where there's money to be made, especially on something as risky and volatile as bitcoin.  


I think how much you believe in bitcoin is also another big factor, but weigh that up with what you can afford to lose. If you believe in the potential of bitcoin and think it has a strong possibility of becoming a huge currency or commodity then put your money behind it. I still believe in bitcoin and think it can rise by many thousands again, but I wouldn't remortgage my house to buy more, but it's certainly something I'm happy to spend time on getting moe of and putting a little extra money in every now and again when I can afford it.