I'm 35 now, almost 36, and am staring to feel old. I'd say around 30 is the time when you start looking back fondly on your younger years. By that time your life is pretty much set. You're probably pretty entrenched in your career, have started a family(maybe), possibley have a house and a mortgage to think about, etc. Prior to that there's always the "future" to think about. Then one day you wake up and realize the future has arrived.In other words, you've made your bed and are now lying in it. Like it or not.