I dealt with depression on and off for about 4 years when I was younger but for the last 10 years I've mostly felt well. However I often get, what i call "downs." It happens more when I'm stressed or bored, or both. So today for example, I had a lovely morning, mainly running errands, but I felt productive and happy. Sat down for a rest after lunch and just got hit with intense feelings of self-loathing, worthlesness etc. and the rest of the day becomes a complete write-off. I'm bored but I cant interest myself in anything, I feel lonely, unlovable etc. Simultanously numb and like I wish I could get drunk to numb out everything. It's like some of the darker points of my depression but it only lasts about a day. I know I'll wake up tomorrow and feel fine. Sometimes it happens as often as once a week but other times it doesn't happen for months. It's seems to be particularly linked to not having plans - though I did have plans for this afternoon.

Is this normal? Does everybody feel like this from time to time or should I be doing something about it? How can I avoid it without just never allowing myself down-time?