For me, I felt terrible all the time.
I would wake up feeling as though I'd had five minutes of sleep.
Or, I would wake up because I'd stopped breathing. My heart was hammering, I was sweating, gasping for breath. I thought my heart would explode.
In fact, feeling that way drove me to the emergency room one day. There, doctor told me I almost certainly had "sleep apnea". I'd never heard of it!
Then I got tested, got a CPAP, and got my life back.