Depression can take so many forms after your mate leaves. In my case I slept and stopped eating.
Let me explain. I've been an insomniac all my life. The first night after Bob told me he was leaving, I slept like a baby. I went to bed at 10:00 p.m. and did not wake up until 8:00 a.m. the following morning. I'd slept a solid 10 hours! And this occured every night.
However, food tasted metallic. I could not eat. And within six months I'd lost 25 lbs. and about 4 dress sizes. Everyone told me how great I looked, but I felt like shit. I felt rejected and lost and rudderless. I had no guidelines and didn't have a clue on how to behave. Just be aware that depression takes on many shapes. The blanket of deep sleep is one of them.
Not eating is another. (Whereas some will seek solace in food.) Just keep on nurturing yourself the best way you know how. Don't play the blame game. You'll hear enough blame from the spouse who is leaving, so be your own best friend. I know. Easier said than done.