I've always had this mindset, and I believe it's what has helped propel me forward in life:
> I am responsible for every single thing that happens in my life.
The power in this mindset is that it eliminates all excuses and makes you the captain of your destiny. The truth is, the vast majority of the things that happen in our lives, whether in the next 10 minutes or the next 10 years is ultimately the result of our decisions. Whenever anything bad happens, I always ask myself: what could I have done differently to have a better outcome or to have prevented that bad thing from happening in the first place? And without fail, there were always things I could've done differently or better. Then I take those learnings and apply them in the future in similar situations to have better outcomes.
Yes, obviously there is noise and randomness in the world outside of our control, but in the long term those things get averaged out and what you are left with are all of the decisions you made in your life that got you to where you are today. Most of the time, I've found that things aren't how we want them to be not because of the things that we did, but because of the things we didn't do. Achieving your goals often requires you to endure great suffering. Most people aren't willing to do that, so they never get what they want.
The alternative is to be a hapless victim buffeted by the winds of fate. That is a terrible way to live life.
Of course there will be some bad things that happen that are really a bolt from the blue. Maybe you're walking on a sidewalk and a car careens out of nowhere, hits you, and you end up being paralyzed from the waist down. Or god forbid you get cancer. But I maintain that the best way to handle any and every situation (including those terrible ones) is to not get emotional but focus on what you can do to make the most of it. At the end of the day, we all have to play the cards we're dealt. How you play them will ultimately decide whether or not you achieve the life you want.