In the finance world it's called hedging your bets. You want to dip your toes in both ends of the pool, just in case.
I've been suffering from insomnia for a while now. I can fall asleep without much trouble. The problem is I only get about 3 hours of sleep before waking up. Then I either cannot fall back asleep, or I go on a cycle of sleeping for 5-10 minutes and waking up again, over and over all night long. By the time morning arrives, I am completely exhausted, I get no REM sleep, and basically cannot function at all during the day.