It's dark out. You can't see a thing. You don't want wait for your plants to grow (see secrets). You want special rewards (see secrets). Try meditating! Go to your profile, and press meditating, and it will fast forward time!
Running out of energy? If you click your profile, it will show your energy bar. You can get tired easily! If you start to get tired, and even exhausted, your happiness will start to go down, and you won't be ably to mine/walk/work as fast. So take a nap! You don't need a bed to sleep (see secrets), so just sleep under the stars! That bar will go right up! Be careful though, you might be attacked by dropbears...