I decided to sell my bitcoins but a week later, the price increased. Should have waited.
This sometimes happens, just can not accurately predict the price and I do not think this is the worst thing that can happen. It is much worse to lose in gambling.
Yes, this thing is true, we cannot accurately predict the next pump up value of bitcoin, so in terms of selling your coin, it is so hard to figure out if it is the right time to sell it, unless you really need it. That was happened to me before. Predication of bitcoin prices is always difficult due to constant up down in the prices.