I cannot tell you how often I have felt the same and described it similarly. You have to simply look at the short term not the big picture. Try to go for a walk, eat something, have a cup of tea, phone a friend or go somewhere where there are other people even if it is just the local park. Sometimes it does actually help just to go to bed and pull the covers up over your head and sleep.

Just try to find something that will help you get through the short term and repost if you need support.