How are you supposed to decide where to get care for emergent conditions? Where is the dividing line between "just book a clinic visit", "head into urgent care when you get a chance", and "go inmediately to the ER"?

So this is a question I've always struggled with and it makes me feel very dumb especially because I literally am a EMR. This feels like something I should know. But at the same time I have also called to book a clinic visit before and had the scheduler tell me to go to the ER immediately only for it to wind up being nothing.

Certain things are obvious of course. Like if I need stitches or there is other major trauma then I know to go to the ER. If it is something like a concerning infection then I know urgent care can sort me out. For a skin rash that's probably a clinic visit. If urgent care is closed and it can't wait then default to the ER. But there are also the issues where I genuinely don't know on what side of the line they should fall. This is especially an issue for things that have been going on for a while which I know could be severe but almost certainly aren't.

For example (not asking for medical advice) I've been having repeated extended periods of heart palpitations for the past 2 weeks. At first I just chalked it up to screwing up my anxiety med schedule while I was on vacation because my med situation does cause heart palpitations if I screw it up. So I didn't think much of it at first but now I've been back on my meds properly for 2 weeks with no change. So, that's cardiac symptoms which in a patient would make me tell them to immediately go to the ER just to be safe. But at the same time it's been going on for 2 weeks and it's probably just some vitamin deficiency or something so it probably wouldn't kill me to wait a week for a clinic appointment (no walk in clinic here). Do I split the difference and go to urgent care? It's like schrodingers medical issue, it's both the worlds most benign thing and a symptom of immediate death until someone looks into it, so how do I know who should open that schrodingers box?

It seems like there has to be some easy dividing line on how to know which one to go to that I just don't know.

Edit: In USA, because that probably matters here.

So I just discovered that I have been working next to the waste of oxygen that raped my best friend several years ago. I work in a manufacturing environment and I know that you can't fire someone just for being a sex offender unless it directly interferes with work duties (in the US). But despite it being a primarily male workforce he does work with several women who have no idea what he is. He literally followed a woman home, broke into her house, and raped her. Him working here puts every female employee at risk. How is that not an unsafe working environment? How is it at even legal to employ him anywhere where he will have contact with women?

I've been seeing a lot of users from alien.top commenting in various threads (mainly sports) lately. They only caught my attention because they are all flagged as bots and I typically manually block most bots (not all because there are some I like). For every one of them their entire post history consists of 1-2 comments or posts. When I took a look at that instance there is nothing there at all and it also shows no users. The comments look human enough but I guess I wouldn't be surprised to learn that all the comments are LLM generated. Is alien.top just someones LLM experiment or is something else going on here?

So I just went and donated blood again and durring the recovery period it occured to me that it takes quite a bit of work for your body to regenerate that lost blood volume and the actual blood cells. Regrowing that many cells seems like it would be fairly energetically intensive. So how many calories does producing all those new blood cells actually consume? Is there even a way to know that?