How do I know what I know?

Many people have come to many different conclusions about life: what is right, what is wrong, what is success. Sure, I've thought about those things, but my main focus has been on why things happen the way they do.
For starters, why was I born into the family I was born into? Well, it's because I needed the culture to be brought to me, and I needed to be surrounded by it too. Both of my parents are musicians, so it was inevitable that I'd be introduced to music and other art forms. these things have altered my life forever, but art, family and how art has impacted me is not what this post is about. This post is about why everything happens for a reason.
Some may say I'm only searching for a comfort level; I would disagree with them, to an extent. I wouldn't disagree fully because a certain comfort level is established, but I would disagree because that's not what I'm searching for. In fact, I wasn't searching for anything when this realization fell upon me. I was actually extremely upset that I had missed my bus and would in turn not get to class on time (I still worried freshman year).
I used to take the Kimball-82 to the Belmont Blue Line everyday to get to school. I had already woken up late so my schedule was all off. After I washed my face and brushed my teeth, I sprinted for the bus. Getting there a millisecond too late was the second bad start to my day, and I let it show. I was angry, upset and annoyed at every aspect of life. I couldn't understand why the bus driver couldn't wait the extra 10 seconds to let me on the bus, but I soon would.
After waiting for another bus, I was still enraged. As we approached the Belmont Blue Line stop, I see a surplus of city vehicles outside of the station. The platform is underground, so I couldn't see what had happened, if anything. After paying my fare, I see police and paramedics surrounding a person. I soon after found out that this was a man that was hit by the train as it passed; he got off the last Kimball-82 bus.
After waiting for the train to clear up, I realized how lucky I was that I didn't have to witness that horrific event.  My anger disappeared and turned into gratitude. I realized that it wasn't that bad that I missed that first bus, because then I would have witnessed a traumatizing event. This is just one experience that I have analyzed, but there have been many more instances that have led me to believe that everything happens for a reason.