There are moments when the mind is running at a mile per hour and it is difficult to remain calm. When this happens, it is more difficult to control thoughts, especially negative ones, a couple of minutes of calm is enough to lower the level where you are. A moment of meditation can be useful, try to empty all those negative thoughts and turn them into positive. Get away from that negative environment because it can help you considerably, think of somewhere you like or something you like to do. The time you spend away from negative influences will give you a space of tranquility.
Take into account all those good things that surround you, no matter how small they seem to be, although sometimes we do not see them or not, we value them. Leave aside so much thinking about the negative and see the positive things you already have and surround yourself with positive people.