Even though I'm not the author, I'll give my answer so take it for what you think it's worth.

I would imagine that what you stated is the correct answer.

People tend to get greedy and just think the rise won't stop and forget to take profits off the table. They go to bed one night and wake up the next morning and lose 90% of what they could have taken off the table.

If you set up stop loses as you suggested you mitigate your losses.

A lot of different TA people I've watched use the fibonacci retracement tool to kind of pick percentages they believe in and take out profits along the way as the coins increase in value.