I write quality articles myself.
I am sure you do, but don't forget to get a neutral opinion too, from external eyes, not your friends or family. We are not always objective about our own work, so it's always good, from time to time, to get such external opinion.
I am an honest writer
Google can't (yet?) measure the honesty of a publisher. So I would say that, at the end, it doesn't matter if your honest or not. But I think it's important, at least for your own conscious, but this is not what is going to pay bills.
That being said, as keyplyr said, check what those errors are and fix them. Also check the evolution of the number of impressions of your pages, and positions in the SERP (this is still from the GSC). You can also narrow these stats by platforms (desktops/mobiles). This might help you understand from where you are loosing traffic.
It's also possible that Google is not finding the "signals" that it is looking for to qualify your content of useful / authoritative / original. Additionally, I keep reading (don't know if this is true) that Google might downgrade health related sites, which can promote unhealthy(!) or dangerous things. If you are in fitness, may be you are on the border line of (un)healthy content.
And in 2018, there are common questions, about, is your site mobile friendly, slow/fast, HTTPS. It might not explain a 50% loss of traffic, but adding little details, can lead to bigger issues.