When you are in high school, the concerns of high school (success at athletic endeavors, popularity and grades, often in that order) are generally going to be a big deal to you. But once you are out of high school, you realize just how little those concerns actually mean in your life afterward. When it comes time to do whatever you really want to do in your life, nobody is going to care how a particular meet or game went, and you are very rarely going to be asked for your high school transcripts. Not to mention the fact that nobody will really care how popular you were (or weren’t).
What ultimately matters in your life is what you do after you have finished high school. While most people end up graduating, the ones who are ultimately going to be the most successful (at least, in 99% of cases) are the ones who have taken their educations to the next level. While you do not have to go to a four year university and get a bachelors degree, you would be very advised to seek some sort of additional training, so that you can get a better job than you would if you had nothing but your diploma as certification.
You need to keep in mind for the most part, people who only graduate high school are not going to do as well in life as those who take on some kind of additional training or schooling. You have a very large number of different options available to you in this regard, but the underlying theme is still going to be the same. You either need to get yourself into a higher state of education, or you are going to be left behind in this world. Getting left behind means living at a lower standard, not retiring as early, and even being in worse health.