Perhaps the sentence is missing a word, and should read: "Love is blind, and lovers cannot see the pretty follies that THEY themselves commit." In this sentence, "commit" means "to do" ("to perpetrate", "to perform". Example: "He committed murder.") Aside from its usual meaning of having a pleasing physical appearance, "pretty" can mean "very bad" ["I lost my wallet and passport while in a foreign country, and found myself in a pretty predicament." = I found myself in a very bad situation.] "pretty" can also mean "large", "considerable" ["He owns a pretty amount of gold and silver." = He owns a lot of gold and sliver.] "pretty" could also mean "apparently attractive, but only superficially." [He's full of pretty words = He says things that seem nice, but really aren't."]. Honestly, it's hard to be sure which meaning the author has in mind. If I had to guess, I'd say "apparently attractive, but really harmful." But to tell the truth, I'm not sure!

Commit, as in commit a crime. It just means the act of doing something that you have done, but it suggests an act of wrongdoing. Also, 'pretty' used in the same sense as 'quite' can only used before an adjective. In this case, a 'folly' is a noun, meaning to make silly mistakes. 'Pretty Follies' translates into more simple English as Pretty mistakes.