The other day, a guildie asked me if I wanted to heal an +18 NW (Necrotic Wake) and I just went for it. It was a depleted key before we got to the first boss. The tank didn’t know it was a necrotic-affix week, and when made aware, he forgot what necrotic was. FYI necrotic-affix is a stacking anti-heal debuff. At 40 stacks of this debuff, any healing spell cast on you will give you exactly 0 health. The debuff has a short-ish timer. As your stacks start to get up there, you will want to slow the mobs and yeet yourself far away so your stacks fall off and allow the healer to top you up. After 3 total wipes, one of our members leaves the group and that was the end of the NW +18.
The person with the key asks if we want to do the 17 key. We stick around and pull it off. The tank had a couple “oopsies” with stack management at the beginning, but got into his groove pretty quickly. We timed it with only a couple of deaths. The whole group was incredibly chill. I know there’s a lot of toxicity in the LFG, but this group gave me a big confidence boost to stop short-selling myself. I should be doing 15’s on the regular, but I still have many well below that. As of the writing of this post, I still have 1 dungeon that is sitting at a single digit key. I will have to fix next week when bolstering is the affix. I’m sitting at a M+ score of 2237. I’m soooooooooo close, I can taste it.
Bodhi Rana 
I’ve never done higher than a +5 I believe. Maybe not even that. Even with a guild group in Discord, the level of stress is too much for me. I haven’t done any since Legion, and after a couple heroic dungeons with groups doing the go go go method, I felt I could even keep up. Felt like as soon as I would get a good position and start ramping up they were pulling mobs dow a hall. So I stopped doing dungeons.
There is the gogogogogo crowd in M+, but there’s a chill side too. The group leader will usually say “chill” or “don’t be rude” in the description. Those groups tend to be really great. Another group are the ones that put “complete” in the group descript. They don’t worry about timing it, they just want to finish so they get something in their vault. These are no stress too.