There is a psychological reason that people can feel fun. The source of all fun and happiness is a set of happy hormones, including serotonin, dopamine, oxytocin, and endorphins, which are body’s natural feel-good chemicals. Doing fun things will release happy hormones into our brain which in turn give us a positive viewpoint on life and can even temporarily relieve pains.
Serotonin can be obtained by eating food with tryptophan (such as whole-wheat bread with turkey or cheese, oatmeal with a handful of nuts, salmon with brown rice, pretzel sticks with peanut butter and a glass of milk), aerobic exercise (swimming, bicycling, brisk walking, jogging, light hiking), bright light, massage, and mood induction (thinking of something good).
Dopamine can be obtained by eating food with proteins, eat probiotics, exercise, enough sleep, listen to music, meditate, and enough sunlight.
Oxytocin can be obtained by yoga, listen to music, massage, share feeling with loved one, spend time with friends, meditate, active (or empathic) listening, cook (and eat) with someone you care about, cuddle or hug, random act of kindness, and pet dogs.
Endorphins can be obtained by exercise, laugh, listen to music, eat dark chocolate, dance, and meditate.