How do I become better at controlling emotions?

Controlling the reaction out of those emotions is more important than controlling the emotions itself. I remember a small story of lord buddha where he requested his disciples to get some water for him from the nearby pond, they bought the water but found that it was not fit for drinking as it was muddy, they informed the same to lord buddha to which he said that it's not at all a problem, let the mud settle down, his disciples were confused at it but after some time they saw the container with clear water where the mud was settled at the bottom. The water was drinkable now. The best way is to let the mud settle. Tell yourself at moments of extreme emotional discomfort that may what goes I will not react immediately and wait for sometime before outbursting, you will see that 90% of the problem is solved for which otherwise you would have regretted. All the best.