For the other question (sentences in general / language agnostic), it's a bit harder to decide. As there's a lot of sentences that are really great.

The one sentence that I keep returning to and that is kind of my life motto is: "this too, shall pass." It's a simple sentence that signify's the fleeting nature of things. It's applicable to every single event or thing in life. It's possibly my favorite sentence.

However, there's tons of other great ones, so it makes it hard to choose... I really like: "Have you ever realized how insignificant your existence is on the planet?" and everything that follows it. It's a quote from the anime Haruhi. The main character asks it, and then goes on to explain how she realized that she wasn't really significant in any way. Everyone was just kind of doing the same thing in all parts of the world. And that there's so many people, nothing is really all that special. It really puts things into perspective.

There's a lot of other good stuff as well, but I think that satisfy's your question :)