In the first season Jay (a slave who spent time living with Indians) tells Ben Pullman that we each have two wolves inside, one good and one evil. Only the one you feed can live. He leaves unanswered which one Ben's father August is feeding. In both seasons characters give in to the their better and worse impulses, but in the second season it becomes clearer how much of a factor the fear inside can be.
There were two conversations that stood out specifically. In one, Noah argues that you can't get rid of the fear; you just can't let it overcome you. That is a healthier attitude than the other conversation.
Elizabeth has had a hard time. Watching the woman who seemed on the verge of a nervous breakdown over her failure to conceive, it was hard to picture her taking to sheltering runaway slaves with such enthusiasm, but she did. She found a new purpose and new abilities, and found herself held hostage in her home, raped, attacked and branded, mocked by her attacker, pelted when attempting to speak, and her husband was murdered.
She was never going to get good advice from Cato, but she had no way of knowing that.
You could certainly argue that the things he was saying didn't sound like the words of a recently suicidal man. There were reasons for alarm bells to go off.
Elizabeth said she didn't know whether to try and keep the fear inside or let it out. Cato's advice was to pull it all inside and then let it all out, transforming you into a worse monster than the one who hurt you, basically.
And he sounded convincing; Alano Miller is a super-intense actor. Shortly thereafter, Elizabeth commits arson, blackmail, and apparently enters into a sham marriage to get inside information in preparation for the raid on Harper's Ferry. She also participates in a daring raid to free the slaves from three plantations with Noah, but she had participated in a daring raid to rescue Noah before a lot of the terrible things had happened to her and before she had ever thought about becoming a monster.
It's worth remembering that Cato's pretended suicide attempt was an effort to gain sympathy to accelerate his spy work in pursuit of Harriet Tubman. When he is buying the freedom of some slaves, and contributing to causes, it can look like there is a good heart there, but there are other clues that his primary motivation is ego. His belief that he is the necessary force to tear the country apart is easily cast aside in favor of controlling the legend of Patty Cannon.
Even if you ignore moral issues (which I don't recommend), Cato is not the best source of advice because he doesn't seem to have much of a problem with fear. He did fear for Devi briefly, but he turned on her definitively when she rejected his actions. His ego may lead him down bad paths, but it also tells him he is smarter and more capable than everyone else (which is not completely unfounded). Elizabeth would never really want to be like him, even if there is some temporary allure.
Caring for others does hurt. Noah's worst taste of fear comes when he learns that Rosalee is pregnant. It was bad enough fearing for her; now there is so much more at stake. It does lead to anger, but still, his answer is that you cannot let the fear overtake you. You might even take big risks to help another family, and other people, because you know that it matters. (Hence a daring raid freeing slaves from three plantations).
If you don't care about anything you don't have to fear anything, but it's no way to live.
You have to find a way to deal with that fear.