I don't thing that there is a behavioral bias for that one.
Maybe its simply that the investor is cautious.
Im just trying to think of scenarios for the exam..
It could be regret minimization. But this is only when you stay in comfortable investments or don't sell profitable ones cause they might go higher and you don't want to feel the regret of missing out on it.
regret is more staying in comfortable investments too long. also with regret you'd tend to pay your expenses with dividends/interest (similar to self control).