The Atom shows us how being small is perfectly acceptable even if it means shrinking to less than a millimeter where you can only be seen with a microscope. On numerous occasions, the Atom has played an extensive roll in thwarting the evil plans of other alien races and Justice League arch-enemies.
Wikipedia briefly summarizes the story from one of the Atom's better known alter-egos, Ray Palmer (originally from the Silver Age):
"Using a mass of white dwarf star matter, he fashioned a lens which allowed him to shrink down to subatomic size. Originally, his size and molecular density abilities derived from mechanisms in his belt with a back up device in his gloves. Much later, he gained the innate equivalent powers within his own body."
So you see, if you're a small person physically or we're never any good at sports because of your physique, it's perfectly okay. Perhaps you feel small because no one seems to listen to you and it seems sometimes you aren't important. Just remember Ray Palmer, the Atom, a man whom actually found a way to harness the some sort of goddamn energy from a white dwarf star to make himself shrink to a microscopic size; using this very smallness to save this world and others time and time again.
Just as the Atom is essential to the survival of the JLA, you as an individual are an intricate part this world as a whole; no matter what your size. Never let a small body or the feelings of smallness stand in your way.
The Atom, Size Don't Matter, White Dwarf Stars, Ray Palmer