A player requires energy to use tools, fish, or engage in combat. When the player wakes up in the morning, they will have full energy, unless they went to sleep at 12:00 am or after, in which then the player will wake up with an energy penalty. If the player runs out of energy, they will pass out where they are currently standing and will be found and woken up, in which they'll have only 1 energy and will immediately need to go home and rest.
Most food items can be eaten to give the player energy. Stardrops can be consumed to increase the player's maximum energy.