one way is writing off your bitcoins as not yours. that money is not yours to spend. just forget about it. the more you look at it, the more you will just want to sell it especially when you see the value of bitcoin.
I don't feel like that. At some point, when you've acquired some wealth, you begin to run out of the things you want to buy.
Of course there are still things I might buy, things I might want, but all these things are things that I don't really need, therefore I'm happy holding my BTC regardless of the price.
Imagine that you have a house. At which point you stop craving for a bigger, more luxurious one? When you have a family of 4 and you have a 4 bedroom house, do you really need to spend more money to get one with 5 or 6 bedrooms? There are many people who don't want to buy new stuff because they have everything, at least everything they can find time to manage.