Those of you who bought in at 10 Dollars of less, how did you not sell early?

Everyone says that "if only i had spent more on X coin when it was X price!" but they forget that a lot of them would have sold early.

so those of you who have held Eth from last January or before, how did you resist selling when it went to 20 dollars but crashed back down to 10? or how did you resist selling at 300 dollars? I'm interested in the resolve it took to hold.

What was the process? I'm in a similar position right now with another coin which i think is going to have an ETH kind of run, but you never really can tell for sure.