The definition of aspire...
to long, aim, or seek ambitiously; be eagerly desirous, especially for something great or of high value.
That's an awful lot for a six letter word. You can aspire to be great, you can aspire to be strong, you can aspire to be successful, I suppose you can aspire to be just about anything. Most of what each of us apsires to be is relative to the rest of the world.
Perhaps that is why apirations are individual. They account for who we are, our character, our charisma, our actions. We aren't programmed to aspire to just one thing. I hope most of us have, at the very least, a few aspirations to obtain. Some for the short term, some for the long term, and even a few in between. I myself have several. All the smaller ones are the stepping stones to the final one, and once I get there, I hope to have more.
Aspirations need to be driven by something, external or internal factors, just as motivation, one is stronger than the other. Whatever it is you aspire to do or to be, it needs to come from within you. External factors can help with the motivation but you have to want it, think it, and desire to be it.