Having turned 30 last year, I don't feel much different than a couple of years ago, nor do I feel any adverse effects of aging as yet. Still, what one can witness on social media is that a) 30 is a milestone that 40 once was and b) it is an occasion to take the time out and reevaluate your life as well as recognize your achievements.
Before you decide to date someone, ask yourself if you'd let me date them. Is he good enough for your sister? Fine, then, go ahead. If not, onto the next one. I mean, people fall in love with you in line at the grocery store. I think it's safe to say there will always be fish in the sea, little sister.