The Stoics were an ancient group of philosophers who refused to get caught up in in the woes of society; they held fast against the ups and downs of life.
Identify what you Control
Stoicism is centralized around control. Having a clear line of what you can and cannot control, (or 'circle of influence') is extremely practical and, as I've found, is extremely motivating. You can't control what grade you get in an exams, but you can control how much you study for it. The delineation is simple, but the outcome is huge; stoicism teaches you self-ownership. If you don't like the outcome, your first thought should be "How can I change this?" not "This is unfair! Why did this happen to me!" (actually asking yourself why something happened might be a good thing, as long as you can answer truthfully). David Goggins is an exemplary example of this. Growing up in a racist town, with an abusive father and no money, Goggins had every excuse to become a statistic, but instead of whining - as he puts it - he focused on what he could do and nothing else, developing him into the decorated soldier and ultra runner he is today.
Expect the Expected
Another key tenant of Stoicism is to accept the 'nature of things': Anything that can happen is valid, and any valid outcome ought not to vex you. Things break, get lost, or even stolen - these are always a possibility and you do not control it. It is futile to get upset with physical realities, you cannot control them and you cannot change them. Furthermore, isn't it just kind of embarrassing to lose your head over something you knew could happen?
When a Stoic breaks their favourite cup, they have already accepted it, making the loss easier to bear.
Hint: You Control Your Emotions Too
At least thats what the stoics believed. They didn't know about the gut-brain axis back then though.
I found that by the time I applied the previous two points, the last came easiest. When you identify what you can control about a situation, you stop feeling like a victim and begin feeling like the master of your fate. Then, with the additional acceptance of reality, situations you can't control don't catch you off guard, creating a powerful barrier against negative emotions. Even when negative emotions (eventually) win, the practice of stepping out and assessing the situation that the previous points require, helps you distance yourself long enough to rewrite the story into one that empowers and uplifts you.
Emotions are ancient, confusing signals but one thing is true, when we do something we think is right we get rewarded - we feel good! On the other hand, when we do things we think are wrong - no matter how good we are at making excuses or lying to ourselves - we are punished, we feel sad, ashamed, anxiety and yes, maybe even depression. These ancient signals don't know how to deal with the modern world, our social groups that we tend to compare ourselves to are now huge, competitive, and highly filtered. We have extremely high quality entertainment available at any moment. That is to say our negative signals are amplified and our positive signals dampened.
Stoicism may be ancient but it's more relevant today than perhaps it has ever been.