I was 18 or so, and in the months following graduating high school, I got a job at Office Depot. It wasn't super hard work, but my trainer got into a motorcycle accident just a few months after I started, and I was essentially the only stocking/supplies person working. So I was working long 10-to-12 hour days, 6 days a week.
On one of those days (somewhere in the middle of the week), my buddy asked me if I wanted to hang out with him after work. This was during the winter months, preparing for Christmas, and surprisingly, Office Depot can get rather busy this time of year (people buying computers and other gadgets for presents). I thought about saying "no," but we hadn't hung out in a couple of weeks, so I said "sure." Who needs sleep anyways?
So I end up drinking a fuck-ton of energy drinks after work, because I've been up for 16+ hours working and need a boost. My buddy says that he's going to make a stop and drop off something for his girlfriend. Little do we know that his girlfriend (some girl he met online who lived across town) is hanging out with her coven of 5-6 other friends (a couple of which were in town for the holiday break from college).
So we encounter their friends, and I really, really like this one girl. I ask my buddy about it later on, and he says that we'd match up really well together... similar sense of humor and all that. So he arranges a dinner for us all to get together for dinner (at an Applebees... I know, classy).
Well, my buddy ended up dating that girl for another year or so, before it ended disastrously. But I've been dating that friend that I had my eye on for nearly 6 years now, we've lived together for 3 of those, and we plan on getting married in mere months. We've already plotted out our children's names, and she is, without a doubt, the love of my life. She has helped me become the person I am today, and is always inspiring me to become the person I want to be. Thinking about a life without her just fucking sucks, and if I had gone home to sleep that day, I would have missed out on the past 6+ years.
So, you never know what you're missing out on when you say "no."