Hey there Puf! Are you feeling any better today?
When you get down, you need to just look forward to the goals in your life. Do things for yourself and look after yourself. If you enjoy massages, go for one. Take your dogs for a walk - they are super at therapy!
Keep your mind occupied with different things, like crosswords or watch happy movies. I also just want to climb under the covers when I feel like this, but becoming all introverted makes it that much harder to climb out of the hole. Don't allow yourself the opportunity to think about your feelings - just keep busy.
I hope we eventually get used to these depressive episodes, as it is something I also really battle with. And it doesn't matter how much I know that it will pass, at the time it's hard to deal with.
Try get involved in a hobby which you can really get stuck into. Take the focus off yourself - maybe volunteer at a hospice or similar. I get a lot of satisfaction out of being able to help someone else