Investors fall into several categories:
Those who do their dd, buy, and support;
Those who buy on a whim and sell on a whim;
Those who are in-and-out traders;
Those who buy high, sell low, and complain;
Those who buy on momentum and cheer on the way up and condemn on the way down even when doing so undermines their own position.
Obviously, some of these motivations are rational and some are irrational.