Logic, especially formal logic, is hard in the same way that mathematics is hard. It takes a certain kind of intellect to be comfortable with it right out of the gate.
I think that the best way to initially approach it is slowly, in small chunks. You can't read a formal logic text as if it was a novel. Read a subsection of a chapter. Over and over if necessary until you can really see and feel comfortable with what it's doing. Then move on to the next bit.
Another thing to try is perhaps reading one of the less technical books on philosophical logic first. (Many philosophical logic books concentrate on non-classical logics or otherwise assume that readers are already thoroughly familiar with propositional and predicate logic. They probably aren't the best choice for beginners.) Find a book that discusses logic in prose rather than symbolism, inquiring into what logic is and some of the questions and problems that arise regarding it. That way you can get your mind around what the symbolism is meant to accomplish before you actually attack the symbolism with proofs, derivations and whatnot.
Something like this perhaps (you can decide for yourself what you like):
https://www.amazon.com/Philosophical-Logic-Introduction-Sybil-Wolfram/dp/0415023181 — yazata
How do I deal with this because I sure don't want to quit? — krishnamurti
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