Thought restructuring means replacing negative thoughts with more realistic and positive ones. At times when we are really distressed this is not easy. You may know you are being irrational but that's not enough to let go of what's upsetting you. Before trying to think rationally you need to try to self-soothe. If you have a hard time calming yourself down, here are some mindfulness techniques to help you through this:
Focus on what's in front of you - pick up an object and focus on it. Pay attention to how it feels in your hand. Try to picture how it was made, where it came from, what the production line might look like, how did they decide on the color or shape, etc. Just keep asking questions until you are no longer thinking about your problem.
Try going outside for a walk - look around you and count how many people are wearing green, drinking coffee or riding bicycles. Pick something to search for. This helps because you can't actively search for something and think about your problems at the same time.
Try saying the alphabet backwards, countdown from 100 by threes (100, 97, 94,...), multiplying by two (4, 8, 16,...)
When choosing a distraction pick something that challenges your mind. I know some people will want to listen to music, watch TV or clean the apartment but I find these to be more passive and may not work as well. You can easily tune out what you are listening to or watching and still obsess about your problems.
Keep in mind that mindfulness is not the same as avoiding or being in denial. With mindfulness you are distracting yourself to get to a calmer state so that you can go back and look at your situation more objectively.