Your questions ask about the hardest part and the best part about "becoming" a lawyer. Those are good questions. And the answers to those questions are quite different from the answers to the related question about the hardest and best parts about "being" a lawyer. Some of the people who have answered your question addressed the "becoming" questions, and some addressed the "being" questions. Each of the answers you were given were helpful.
For myself, the hardest part of "becoming" a lawyer was providing for my wife and five children while I attended law school. The best part was law school itself. I loved the intellectual stimulation of learning the law and pushing the boundaries of what was known, into the still developing unknown of the law.
The hardest part of "being" a lawyer was the time commitment that law firm life requires. The law is indeed a jealous mistress. The best part was having challenging cases that required both a mastery of a complex set of facts and of a very specific area of the law. Some types of law practice require an attorney to move through cases quickly, repetitively applying the same basic law to slightly different facts. I was blessed to be involved in a practice that allowed me to delve deeply into the law. That was the best part.
I hope these answers are helpful to you as you consider a life in the law.
The hardest part of becoming a lawyer is the Bar exam. Passage is required by all states to practice.
The best part of becoming a lawyer is the people you will meet in law school. They will provide you with thoughtful discussions during and a network of people to rely on the rest of your life.
The best part about becoming a lawyer is gathering specialized knowledge that people really value. Every person and business could use the help of a lawyer. It feels great when people rely on your expertise to make decisions.