What is the average lifespan of a human?
Averaging the numbers from third world and first world countries, you get about 71 years (worldwide).

How many days does that make?
71X365+18 (days added for leap years) = 25933 days.

How many days have I uselessly wasted oxygen?
About three weeks (21 days).

What percentage is that of my life?
0.08%

This feels fucked up. I sit, eat, breathe, lounge around. No purpose. And I've wasted 0.08% percent of my life. This is a cause for a small panic.
This is why I am starting the driving lessons again, very quickly, to try and get my license in time, before I go to Cuba. That way, when I come back, I wont have to start all over, my license will remain valid for another 10 years.
I mean, it is not like I have been completely useless. Wait. No. That's not true, I'm just trying to feel a little bit better about myself.

Never mind, continue with your life.