In terms of having an actually good memory and looking back on past unhappiness and being weighted down by it and thus wanting to compile happiness/happy memories in terms of thinking about the long term future, it isn't always the case that thinking about the long term means putting off "fun" while short termers instead focus on fun right now. The decision to have "meaningless" "fun" right now can be based on long term thinking. Some fun right now, to some extent, is indeed crucial to what one will be in the long term.