You only have time to do a few things. In fact, you only have time to understand a few things.
Life is short. And getting pretty much anything done takes time, often a surprisingly long time. In the words of Piet Hein, "When you feel how depressingly slowly you climb, it's well to remember that Things Take Time." See also Hofstadter's law: "It always takes longer than you expect, even when you take into account Hofstadter's law."
Unfortunately, people often try to do too many things. They split their attention between so many different projects that they're doomed to leave many of them incomplete, or do many of them badly. Or, perhaps worst of all, people do so many little, unimportant things that they don't have time to do the bigger things that they actually want to do. Have you ever found yourself saying "I'd like to, but I don't have time for it"? Maybe it is something better left behind. There are many more things worth doing than you could ever do; there's no shame in not helping a good cause, although every charity and activist would like to believe otherwise when it comes to their cause. On the other hand, maybe it is one of those important things to you that you should make time for, not by trying to squeeze it into your already packed schedule but by getting rid of some less important things.
A related subject is the problem of being informed. I think there is a perception that it's everybody's responsibility to be informed about everything. This is completely unreasonable. You can be aware of current events, but no one person can be enough of an expert to make good judgments about all of who to vote for, how to vote on ballot propositions, the age of the earth, the efficacy of vaccines, gun control, drug policy, healthy eating, optimal exercise regimes, web design, home maintenance, car maintenance, etc. You can only be an expert on a few things. For everything else, the most you can do is follow an authority figure you otherwise trust. Like, I don't believe the earth is 4.5 billion years old because I have a deep knowledge of the relevant cosmological and geological research. I believe it because, whenever I don't know any better, I put my faith in the Scientific Consensus™. The relatively few subjects on which I have my own opinions are the ones in which I've invested the time to be genuinely informed.