Relationships are very much like so many other aspects of life and health. It’s possible to have a solid healthy relationship going through some rough spots or to have an unhealthy one that doesn’t show any outside signs of the real problems. I think a good analogy is comparing it to a body part. You can injure yourself, and it will be painful, but if you’re generally healthy and you take appropriate steps to help it heal, it’ll be fine. OTOH, you can have a pesky joint that you don’t take care of, often take medication to keep healthy and just sort of live with because you more or less forget what it should feel like, and it prevents you from going out and doing the activities you really want to do. At times, the former will seem worse than the latter, but it’s not really so true.
And as for internet advice, well, it’s always important to remember that whoever is telling the story, despite their best efforts, can only tell the story from their perspective. If they don’t see the other person’s motivations and thoughts behind their actions, it likely won’t come through when they tell the story, and it makes the other person look worse. And, of course, anyone responding to it will have their own spin based upon whatever baggage they have in their own lives, perhaps filling in a gap with how someone in their life who behaved the same way did, or whatever. It all needs to be put in perspective and taken with a grain of salt.
I do think internet advice is useful though, largely because it gives one perspective on their own perspective. That is, if one is thinking that maybe his spouse is cheating, well, it’ll be obvious that that’s what he really thinks is going on when people respond with “OMG GTFO!” That is, it’s more like that old flip a coin trick when one isn’t sure what decision to make, to flip a coin and whatever side they hope it lands on is what they want. Here, it tells him what he’s really thinking or perceiving, it may or may not be true, but it gives him an angle to approach the problem. So, in such a situation, he shouldn’t immediately assume that she’s cheating, but it is a sign that there’s a problem with perspective and trust, and he needs to look at that.
So, yeah, it can be helpful, but it’s far from a direct end-all-be-all sort of advice.