Alcohol is definitely not the answer to the "how to control your emotions in a relationship, at work, anywhere" question. Some people start drinking because of their too-hard emotions. You need to know that it doesn't help and it only makes the problem worse. So better just don't drink alcohol at all or drink it as rarely as possible.
If you are spending time in a company of your friends or any other people and you feel that it's too hard for you because of your hard emotions, and you don't know how to control emotions at work, don't be afraid to leave and spend some time alone. It is your right and it is much better than staying there in a bad mood.
If you are a sensitive and emotional person, you can be the happiest in the world as you get happy emotions brighter than other people do. So why not to give them to yourself every day? The best way to control emotions is by doing the things you like, e.g. watch movies that you like, go to concerts and plays, visit friends and do everything that makes you happy, at least one such thing per day.
When you feel that you are reacting too hard, as a way of controlling negative emotions, try to take a deep breath for a few times. It will calm you down a little, so it will be easier for you to control your emotions.
If you are not sure how to control your emotions, try the PMR (Progressive Muscle Relaxation) technique. It helps you to identify hidden tension throughout the body and, as a result, to become more relaxed and to control your emotions easily.
If you are not sure how to control your emotions in a relationship, at work, etc., try creating a safe place in your imagination. Some people find this technique very effective for them, others just say it doesn't work. Try it for yourself and see if it's effective. You just need to imagine a place that you really like and where you would feel safe. Each time when you get a hard emotion, close your eyes and imagine yourself in that place. Take a few deep breaths. Open your eyes. Is it easier now?
If you feel hard emotions too often, it is better for you to be as relaxed as just possible all the time. Caffeine won't help you with controlling negative emotions, as it has the opposite effect, so it can actually cause some of the emotions you want to get rid of. So better just stop drinking coffee and black tea.
It may sound weird, but a group of people claim that it worked in their case and they consider it the best way to control emotions. When you feel a hard emotion again, try to scale it from 1 to 10, where 10 is the most intensive emotion. Think about it for some time and then take a deep breath. Once you give your hard emotion a scale, it becomes more manageable and easier to cope.
There are days when it seems that everyone is trying to annoy you. Take a moment and think to yourself, could it be true that everyone around you made a pact with each other for annoying you? Unlikely. So just understand that it's only in your head and try to be more empathetic and remember that controlling your emotions before they control you is much better.