I've found that with friends or potential relationships I'm highly selective as per who I let in or not.
I'd say it's oddly like how I view food. Some wonder why I rarely stray from the select foods I eat. But, why try new foods when you can have a perfectly awesome and tested meal that you know you'll love?
I'd rather spend my time and energy with something I know I'll like.
Oddly, I view people with those same standards as well. I can typically tell immediately who I like or not. There isn't that many people I feel that way towards, but I'd rather pursue that than waste my time with someone I don't feel that way towards.
Would you say you're highly selective of the people you let into your life?