What are limits?

KH is making me think.  And like web-surfing, it starts with a brain-ramble about a narrow topic, and eventually burgeons into something that's like "How did I get here, exactly?"
Anyway, I was thinking about targets, and limits.  I set some targets that I think are the upper limit of my potential.  But I don't really know what my limits are until I hit them.  But then how can you set a target?   I don't want to limit to short term thinking only, and don't want to set the bar low. But I don't want to set goals I will consistently miss, or are unattainable. I like small wins.
Anyway, .... it does not really matter that much (.... and yet here I am diary-ing about it), but I DO like to think.  I don't know if I like that I like to think....(brain ramble, here we come...)