How can I keep my mouth guard from falling out? Almost every morning I find my mouth guard in my bed instead of in my mouth. It's not protecting my teeth much that way! Any ideas on how I can keep it in my mouth all night? .

Until. OTC night guard? Useless, best to discard as can do actual harm. Made by Dentist? Schedule adjustment/relign/remake. Until then use small amount of denture adhesive. Also take 1 200 mg Ibuprofen before bed w lots of liquid.
Get a new one. If you wear a mouthguard at night it should be made by a dentist, not something you buy in a store. The dentist makes them so they grip the teeth firmly and can't be dislodged accidently and spit out while sleeping. If your mouthguard was made by a dentist, i would make an appointment with them to have it fixed or a new one made. A good fit takes some effort to remove, it shouldn't just drop out!
If . If your mouthguard is made of acrylic, your dentist can "reline" the inside of the nightguard so that it fits a bit more snugly on your teeth. Your current guard may not fit correctly after extended use, so it should be evaluated.