I think two things I would regret missing would be 1) Time, and 2) Chances.

Time is a valuable resource. Once past there's no turning back. Who is really capable to twisting the gears of the universal clock to sometime where someone wanted to live in? Nobody has that kind of control. To all those dreamers out there who wished there was a time machine, and that things would turn out the same again, the possibility that they will not is 99,9% (to 3sf). I dislike sticking around with people who just usurp the energy from others to listen to their complains, nonsense, or idiosyncrasies. Not making your life any more valuable in anyway. I have better things to do, that's why I think I'm the kind that'll rather save the time for people who I really want to spend time with, which explains the company of friends that I choose to hang out with. However, time can still be controlled, or managed to a certain extent. Time cannot make use of us, but we can make use of time. So, it is vital that we have the opportunity to do what we want, when and while we can do it. Having control of time and the activities you plan around yourself shows that you are somewhat in control of your own life.

Chance, or opportunity. Is like luck. If you are lucky, you meet with it so many times, if you are not, you just don't. But sometimes when one meets with one but hasn't got the timely moment to seize it, or when one is waiting for chance to arrive but doesn't know until he missed it, that chance just vanishes, like that. It is not up to one to factor when it should next present itself, but rather I would conceive it as a series of well linked/planned/thought actions that resulted to obtain this certain consequence/result/chance. Anyway, what I believe is that chance rarely do occur to you, prompting you to take it. Hence I feel that I'm the kind of person that will treasure every opportunity that I am presented to. But because of that, sometimes I feel so fortunate that such chances have made my life so much fulfilling (busy) and interesting (full of activities to keep me occupied). Maybe its the zest of life too.