My most effective life hack has been to learn to be with my inner experience, just as it is. It changes everything.
Unfortunately, most people want a more complicated solution and are dissatisfied with that answer.
I just sit with that. :)
What makes your mind stronger, and more able to control your emotions, is internal discipline and toughness. No one can teach you this skill; you cannot learn it by reading about it. Like any discipline, it can come only through practice, experience, even a little suffering.
The most effective way to learn is by tuning in to the subtleties of your internal experience during the vicissitudes of daily life. This is especially true when you feel reactive, frustrated, or triggered by something or someone, as these are usually the moments when there is the most to sense, track, and feel.