10.

This one's interesting. "That" is there because...Um... It's a big sentence?... All I can say is, without it, the two halves of the sentence seem shoved into one. Research Clauses, Subjects, and Predicates, if you want to learn about english "commas" ( , ) , and our weird conjunctions, and what makes "that" needed here... "you get", here, means you gain, you obtain the motivation... (This sentence COULD be phrased, much simpler, as "Because there are stronger people around, you get the motivation to improve." OR "You get the motivation to improve, because there are stronger people around."). Starting the sentence with "It's" is what makes the "that" needed. It's saying, if you're surrounded by people that are better than you, you feel like you aren't good, and that you need to "catch up", or you feel like you are behind everyone else.