Trust your anger is dubious advice. If you apply the necessary disclaimers, it's fine, but, again, I don't get the sense that the author is balanced in this area.
It doesn't matter how right you are when you're hurting yourself. You're the only one who lives your life, the only one experiencing your feelings. The worse you feel, the worse you feel, and that's it. It can be helpful to let negative emotions drive you, but if you don't walk a razor's edge, those negative emotions will consume the things that make the effort worthwhile.
Life is a gift. Hardships are interference. At times, you have to deal with interference to get back to enjoying the gift. Maybe you're dealing with the interference on behalf of someone else so that they can better enjoy life - noble, for sure. But, the interference can be so ubiquitous that we center our lives around the interference, and here is where we lose the plot. Perspective allows you to see which interferences you need to deal with and which you can look through. Imo we're not really evolved to deal with the world we've built for ourselves, so it takes a good deal of reflection to gain a working perspective. Without that reflection, life can seem like a train of tragedies.
More of a rant than I meant, but take care of yourself. Take care of how you feel and see the world. No one can do it for you, and you're the one who has to feel the way you feel.