The Clinic is open Monday through Saturday, 6AM to 6PM. The Doctor and Nurse will help you if you become sick or if you are weak.
Getting sick and weak is a very easy thing to do when you're working hard on the farm. Every time you do a strenuous activity, you loose a little bit of energy. Your farmer will eventually give you a visual status of his or her energy level. Note the pictures to the right - the first stage of exhaustion is at the top and the last stage is at the bottom. After the last stage of exhaustion, the farmer will not do any more strenuous activity until he or she gets rest or eats some food. You can use the Hot Springs in the Backhills to recover some energy or head over to Rosie's Restaurant and buy Orange Juice, Apple Juice, the Daily Special, or Cake.
Strenuous activity consist of doing some sort of physical labor. Typically it is when you use one of your tools like the Hoe or Axe. You also use up energy when you plant seeds or brush your animals. One activity that doesn't use up energy would be simply picking something up with your bare hands. You can pluck weeds and pick produce without becoming exhausted.
To gain a higher energy level so you don't become exhausted so quickly, you have to find Power Berries that are located throughout the farm. Power Berries are found while hoeing your fields or pastures. There are 10 berries total, and once you find a Power Berry a flower will bloom in the flowerbed (the "Secret Garden") directly south of the Farmhouse. That way you know how many berries you have found so far.
Power Berries are not located in one certain square in the field, they're scattered randomly in the fields. For example if you have plowed up all of the land and haven't found the few last Berries yet, you have to continue to plow up the land you already hoed in order to get the Berries to show up.
You will also become sick if you are outside working hard while it is raining or snowing. The bad weather won't wear on your energy level, but there is a very good chance if you exhaust yourself while working outside in the bad weather you will become sick. Being sick is never fun, and if you become sick you spend the day indoors in your bed. Your animals aren't fed which means they will be pretty unhappy with you for 3 days. You will be fine the next day.
That's where the Clinic comes into play. It's a good idea to visit the clinic at the end of the day, between 5pm and before it closes at 6pm. If the Doctor and Nurse determine that you are sick, then they make you spend the rest of the day (and night) at the Clinic and release you the next day. If you went to the Clinic before you fed your animals or finished any other activity you may have been working on, then you won't be released until the next day. Then you have grumpy animals and a whole day of planting wasted. Staying overnight in the Clinic doesn't save your game though!
You don't have to visit every day. If your farmer reaches the last stage of exhaustion and you are finished for the rest of the day, then you can head over and stay the night at the Clinic. If you are out chopping wood and smashing rocks in the rain, it's a good idea to visit at the end of the day as well. The Doctor and Nurse will let you know if you are sick or if you are healthy. If you are healthy, you can just head back home and go to bed withough worry that you'll end up staying in bed the next day.