I experience that same thing and have been looking for answers as to why it's like that. I get the most crashing depression and anxiety when getting out of bed. Yet, I feel much better during the day and night. What's weird is that I get those feelings more on Saturdays & Sundays (the days I don't go to work).

I read somewhere that, for the mornings, I can be dehydrated and hungry (possibly low blood-sugar) and that's why I feel bad. Makes sense since I can go six or more hours without food and water. How would you feel if you go six or more hours straight during the day without food and water?

One time someone told me that the reason why I feel better at night is because, even though I get dreaded feelings, I made it through the whole day without much going wrong, at least the major stuff. That makes sense to me.