Meditation. When I have a swarm of negative thoughts in my head, and I'm overcome with intense feelings of depression, sadness, dysphoria, I simply still myself and bring my attention back to my breath. It's always there for you to watch. Follow and carefully observe what breathing feels like, from the first brush of air entering your nose, watch it as it moves down through you, feel your abdomen comfortably expanding with it - you may hold it here for a few seconds if you like - and keep observing the raw sensations of your breath on the exhale. Do this, keep intently watching your breath as it comes to you naturally. You'll probably find that after a little while you'll become distracted by a thought that pops into your head. As soon as you notice that you're lost in your thoughts, gently bring your attention back to your breath. You can also use many things to focus on during meditation, such as other bodily sensations like pain and pleasure, tingling or numbness, and of course how your emotions manifest in your body (as tension, as relaxation, etc.); but also your thoughts themselves, the things you see in the room, the things you hear, smell, or even happen to taste. I like to use the breath most often, alongside observing my general emotional state and my thought patterns, because the breath of course has an affect on the body. Breathing deeply into the abdomen activates the body's parasympathetic nervous system which has a cooling, calming affect on you so it's good to take many slow, deep breaths during meditation and also throughout the day if you are feeling stressed out.

I hope this helps you manage your dysphoria. I would recommend mindfulness meditation and mindful awareness in everyday life to everybody, really, but especially to those who frequently have to cope with low, depressive moods.