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.
Pessimists see problems. They worry about what could go wrong in the future. Optimists see possibilities. They focus on what could go right in the future. Proactive people turn problems into possibilities. They give us reasons to be optimistic about the future.
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.