Arguments for: 1) You're young and full of energy, that's the right time for having fun.
2) Later you have no time for having fun, as you have other
anxietys.
All emotions are brighter in youth.
Arguments against: 1) If you always have fun, you may loose, waste your time (could be spent on studiing, family, even work)
2) You usually spend money on fun, that's not great if you have financial problems.
P.S.: good luck)