There are two things that I heard about before, but didn't fully understand until now
The first is the idea that we don't live in a fairly tale, and more often than not, our hopes/dreams/plans are not realized. It's not the same as the concept of "unrealized expectations" as discussed before, but simply that disappointments do come and the best protection is just to brace oneself. At times it's things that you thought "Oh, this would never happen to me, only to other people!" that end up happening to you. Yet as bad as things get, it will never be as bad as we think it is -- we are much more resilient than we believe ourselves to be. Ultimately we make it through and, looking back on those disappointments, there's a sense of gladness for how they happened. You're stronger because of going through the process, more experienced and better equipped than before. I'm not saying that it doesn't suck to be disappointed when those hopes and dreams we cherished fail; it absolutely does, and sometimes you just want to crawl into a hole and....sleep away the pain. But we don't realize that there's light at the end of proverbial tunnel until afterwards. For these reasons I really like Conan O'Brien's words at the end of his show with NBC: "Nobody in life gets exactly what they thought they were going to get. But if you work really hard and you’re kind, amazing things will happen."
The second is the fact that as we grow older, we form habits and thought patterns that are difficult to break. We tend to get stuck on certain things and there's this nasty little thing called "pride" that goes into overdrive. Due to our pride in our own abilities and character, we are consequently less open to change as well as criticism from others. As I look at my older friends as well as at myself, this is my new realization. I find myself these days tending to take criticism from others rather personally -- and justify my own reaction as the other person "being inherently wrong" and needing to be adjusted in their reasoning. But looking at these instances, I'm actually the one in the wrong and the stubbornness only inflicted damage on an otherwise positive relationship. It's also true the saying that only those who truly care about you will try to correct you when you go astray. I hope that for this year and especially in later years to come, I will remain open to criticism and changes around me -- and to me.