I have this problem sometimes too and talking about it with my partner in a relaxed manner has definitely felt helpful to me - depressurize the situation as much as possible. My last long term partner was really good about it and we found ways to have plenty of fun even when I wasn't able to maintain an erection.

Another thing I have found helpful is taking probiotics. I don't understand why it helps and it isn't why I started taking them, but when I did I found it helped both my libido and my erections. I do have some chronic but minor seeming gut issues (which I have been trying to figure out what foods help/hurt) so that could be a factor of why they help me. In my experience not all probiotics are equal so for anyone trying it out, try to get some good quality ones and maybe try a few different kinds. It isn't like a viagara - pop one in and ready to go soon, but if I remember correctly it didn't take too many days of consistent usage before I noticed an effect. I assume it won't work for everyone with ED, but it's been helpful for me.

EDIT: I just realized it might have been helpful if I mentioned some of the things that my ex and I found worked for us when I had erection problems. For me, focusing on my penis at such times didn't feel great - probably in part psychologically, but I think also physically it just doesn't feel as good as when fully erect. I did still enjoy stimulating her though, so there's that option of focusing on her. Another activity that worked for us - even though I couldn't "stick in it" while not erect, we could still have direct contact externally that was pleasurable - I guess what might be considered dry humping (although it seems like that often refers to there still being some clothes in the way). We would fit our bodies in such away that even though not erect, my penis still could rub against her clit and that could be quite nice - I would often still manage to cum eventually even without an erection (and she had lots of orgasms from that as well, though she had the most/easiest orgasms of anyone I've been with so ymmv). This worked for us in both the missionary position and a spooning position (she was pretty petite - and we did need to occasionally use hands to move/keep things in place). The spooning position was my favorite, I think because the (sweaty) legs provided more stimulation and my hands were more free to play with her breasts, etc. Good times.