I do not think that anyone should gamble their Bitcoin away when going up or down. But we are only human and I cannot say that I have not ever gambled in my life as well...

Personally, I play more when Bitcoin is going sideways, just out of boredom. But when Bitcoin goes up, I also feel like splurging a bit, so I might gamble during ups as well. During down price movements, I feel it is better to not do anything with my Bitcoin, just because it seems like a huge waste for when it goes up again.

Although there is a psychological point which makes Bitcoin more disadvantageous to gambling, than with say, paper money. Its because all we see is a number going down or up. We do not see the physical representation of that value. Which in turn makes us more willing to spend or waste more money.