I have read this post and though I could share some of my own experience to motivate you.
When I was in high school, I was an awful student. Looking at my high school grades, I feel embarrassed (WELL below average in my country). On the other hand, I was a good athlete (international competitions) and was extremely close to get into some Ivy League schools based on my athletic achievements. A lot of coaches wanted to get me. However, it all ended up in me getting dinged which was probably the biggest disappointment in my life. I was extremely close but I ended up not getting in because I was short like 50 points on the SAT (the one that has max 2400 points). I did not have the time to retake the test so that was it. I also had enormous pressure from my parents to get in college ASAP.
As a potential international student for a US college this was a huge blow for me. I heavily depended on that money that only big schools could afford to grant. So at some point, I thought my chances of going to US were gone but out of the blue I got into a small private liberal arts college. I got a full athletic scholarship. At first I was kind of uncertain as to whether I want to go to an unknown school. After some thinking I decided to join the school.
I can tell you that this was the best decision in my life. Why? There are many reasons.
I realized that to get into a "big game" you have to go step by step. My lack of commitment in high school cost me a lot, even though I knew I had the smarts. So as a freshman in college I told myself that I need to start all over. Get heavily involved, get high grades and make no excuses for not achieving your goals. I was able to excel wherever I participated, though many time I thought dying feels easier. My point is that from a below-average high school student that had no extracurricular other than athletics, I became a whole new person. Because of my changed approach, my life dramatically changed.
Now that I graduated, I have got a nice job offer starting in January/February and I am actively working on my plans to get into a good MBA program. Just in a few years, the hard work has finally started to pay off. Slowly, but I can see it coming. If I do not get into a good MBA program I will get into the best I can get. I know I will adopt the same approach (or even tougher) when I start my grad school.
As you can see, not going to a top school does not mean that you cannot significantly change your life. Sure, it is always nicer to graduate from Harvard than an unknown school. But going to Harvard will not guarantee success to you, it will only increase your chances. For example I know a guy from Harvard who cannot find a job that they deserve. True story. On the other hand, I was passing rounds at the top US banks (I ended up not getting jobs, but the remaining candidates were like 5 years older and had more experience). As you can see, graduating from unknown school will land you nice interviews if you excel. Getting excelled is your decision to make.
If you do not get into a top school, it does not mean anything. What matters is, what are you going to do when you are in school. My coach said this many times in practices: "The higher the stimulus, the better the adaption." Are you going to study a few extra hours or watch your favorite movie? Are you going to try your best to obtain a leadership position at the school so you can learn something more? I could give you hundreds of examples but you get the point. Get out of your comfort zone and work on your future
Finally, from my experience, I believe that the key to finding success is having enough information. Be tireless when you are researching schools, jobs etc that interest you because it will affect your life. This forum is amazing and while I have a few dozen posts so far, I am reading posts for almost three years. I started looking for the information in my sophomore year to be ready when the time comes and stumbled upon gmatclub. I cannot even explain its impact on me. I am sure it can happen to you if you stay committed.
I hope that you perceived my tone as positive. I am trying to share my experience in the hope it motivates you. Find your course and hang in there. You can do it!
Set your aims high, carpe diem