They always say it's good to force yourself to get out of your comfort zone. Similarly, when one is feeling depressed and down, it is very challenging to even feel motivated to do anything and one gets very "comfortable" in that state of misery or depression or just simply negativity. With me, what works is to force myself to do things. Even if they keep failing and I still end up feeling the same, at least I know I tried.
I think I'm kinda experiencing a bit of this the past few days but I refuse to say I'm depressed if this is truly the case. I'd like to say that it's just one of those down phases. I usually just ride it out, let myself go through it but at the same time try to watch out that I don't overstay in this position for too long? So I try to find things to do that I'd normally feel good with. Gaming, watching funny videos, watching a series, watch a movie, take a walk... I tried these yesterday and I only managed to do each of them for less than.. 15 mins? It was hard, to make yourself do something you're not motivated to do and wanting to just mope around. Not to mention the restlessness that could come along with it, it's all a bad combo if you ask me.
At the same time, you'd tend to like have all these negative thoughts and negative talk in your head, talking you down or discouraging you. I try my best to block these out by keeping occupied. There really is no other way to me. If you're already unmotivated to do things, and you have all these thoughts in your head - that's a full recipe for disaster. When I get sucked into negativity, I always feel badly afterwards, especially if my behaviour was affecting people around me. I always use this to remind myself not to get sucked in - although sometimes, I'm just not strong enough to keep to this.
So, as difficult as it sounds... make yourself do something and keep trying to do something until you settle with one thing that keeps your attention long enough. I know I struggled a little yesterday, and I think I still am (which is probably why this post is so long now), so it's really normal to feel this way. But good luck trying, I hope you'll manage to be a little bit more positive soon.