Most people have no idea what amateur athletes go through to get to the Olympics. It's brutal and you have to love what you are doing. Let me tell you what it is like to train to go to the Olympics.
You will train almost every day. Your Friday and Saturday evenings will be spent preparing yourself physically and mentally for your next training session. Sleep will become a priority for you. Your nutritionist will tell you what to eat and you will eat it. Your coach will tell you what to do and you will do it. Coaches take you to the edge of your physical and mental limits. Goals will be set for you to attain. If you don't meet those goals, your training regimen will be increased. Often times, coaches will push too hard. That's when you have a sob fest and talk to your sports psychologist. When you're finished, you get back where you left off. It's not for the weak of constitution or the weak of flesh. You need incredible mental and physical fortitude to stick with it. You have to believe in yourself and always have a winning attitude. Doubt or negativity is toxic. There is no place for it in training.
You won't have much of a social life outside of hanging out with the people you train with. That's because most of the friends you have now will get tired of you being "no fun anymore" and not being available when they want to go out.
Your body will be sore every day. You will learn to ignore it and work through the pain. Physiotherapists, chiropractors and massage therapists will be your new best friends. You'll get to know them very well.
You will have to work a part-time job and train 5-6 hours a day and live on next to nothing. You will have to try to find sponsors in order to survive unless your parents are able to subsidize your efforts.
When you are in heavy training for a competition, you won't answer emails or the phone because you won't have time. This means you isolate yourself and concentrate only on the task at hand -- training and perfecting your craft.
You need to choose a sport that you love to do that you know you can do over and over and over again without losing interest, as well as choosing a sport that your body type is suited for. If you have OCD, that helps.
Ultimately, you have to have that special something to pique the interest of a coach. They don't have time to waste on people who aren't serious about it. You really will have to give up everything. That being said, it's not an easy life. Most athletes spend 4-8 years training BEFORE they make an Olympic team.
If you are interested in long distance running, it may take that long just to develop the aerobic base necessary to compete as a world-class athlete. That entails maximizing lung capacity, heart strength and lactate tolerance.
Bottom line: If you are not prepared to dedicate yourself completely to your chosen sport and to sacrifice EVERYTHING, you probably won't make the cut.
I'm not saying you never get to have any fun. You will. It's just a different kind of fun
Good luck, and keep us posted on your progress.