The way that life works is both interesting and bizarre. From birth to high school, life is relatively innocent. You live with your parents, and the world around you is dictated by school and friends. Your parents tell you when to go to sleep, what chores to do around the house, and what you can and cannot do. You see the same groups of people every day and you live in close proximity to them. All you have to worry about is making your parents happy and finishing your assignments on time so you'll be able to hang out with friends during the weekend. Life during that time is fun and carefree.
The world will not always stay the same, though. After you get out of high school, everyone will go their separate ways. Some go to college and further their education, in an attempt to specialize in a certain field and get a job after graduation. Others choose to delay the jump into college, or not go to college at all and take a year off from school. Others will work full-time or start a business of their own, and some will even get famous through some bizarre invention that they've created.
Regardless of whatever path you choose after high school, it's weird how life works. In elementary, middle, and high school, everyone is connected to each other. You and your classmates are dealing with that annoying English teacher, talking about crushes or going home after school. You always see your friends in school, and you get to see your family at the end of the day. You have a solid support system, and the world is predictable and easygoing.
Once you get out of high school, however, life changes for everyone. Your friends decide to take different paths in their lives, and you have your own direction to follow. Depending on wherever life takes you, you could get bogged down by responsibilities like paying bills, maintaining your house and just fending for yourself in the world. Your friends could take care of sick family members, develop their careers and deal with dilemmas of their own. The directions that your friends and family take after high school could result in lost connections with each other, and it becomes harder to be around your childhood friends.
Additionally, life happens at such a fast rate. You'll be playing Super Smash Bros. with a trusted friend, having a good time, then you'll be an adult with bills to pay, groceries to shop for and figuring out how to balance your money. You will go from one phase of life to the next one, and it happens so rapidly that you'll express disbelief at how far you've come.
In general, life just changes so quickly, and sometimes you don't have the time to process it. Everyone takes different routes, and even family members will be separated from you, too. Life makes you think that these jovial times will never end, then it smacks you in the face with all of these huge, undeniable shifts that turn your world upside down. Suddenly, life becomes far more serious, and it becomes apparent that your world will change, whether you like it or not.
Overall, life develops in unexpected ways. One moment, you're joking with a friend and making plans for the weekend. The next moment, you're in college and that friend of yours has decided to move to a completely different country. Life does not wait for anybody, regardless of what the conditions were. Life will switch from one mood to another at the drop of a hat, and you might not even notice the change until it's too late.