During the game you use up stamina when you do things such as hoe the ground. There are three different levels of being tired. That's not the only way to tell your character's stamina. There is a face in your menu. As you do different things throughout the day, the face will change! It's important to pay close attention to these faces.
Red happy face:
This is what you start out with. Your stamina is 100%.
Red straight face:
This appears after your character begins wiping sweat off his brow. You're still in decent shape, just feeling a little bit fatigued.
Yellow straight face:
This face appears after your character leans over to catch his breath. Eating something to restore your stamina would be a good idea.
Blue unhappy face:
This face looks kind of scrunched. When it appears it means you can't work anymore. You can either eat some stuff or go to the Goddess and wish for fatigue.
 Levels of Exhaustion
Wiping sweat off your brow:
This is a warning sign that your character is getting tired. You might want to consider eating something such as a fruit to restore stamina.
Leaning over and breathing heavily:
You should immediately eat a fruit or something when your character does this. He doesn't have much energy left!
When your character does this he doesn't have any more energy. If you want to work again you must eat quite a few things, or maybe drink some stuff as well.
- Never let yourself get too fatigued. If you get to the third level of stamina loss, you have a really good chance of getting sick the next day.
- ALWAYS keep something to eat with you. It doesn't matter what it is. This way you can eat when you start getting tired.
- Powerberries increase your overall stamina. Try getting all of them so that you can do more work before getting tired.