I think dismissing the end of a 13 year relationship with the "plenty of fish in the sea" argument and saying "stop wasting your time" is probably not what OP needs to hear right now.
I'll piggy-back off this to remind people that when someone shares something, they are not necessarily asking for your advice. I know HN is a crowd of problem solvers, but it's OK (preferable!) to simply respond with empathy. If it's not clear, consider asking the person if they'd like your advice before immediately jumping in to try to fix it for them.
When a man invest in love it is very hard for them to just walk away from it, to the extent many of them hold on to it, when the reality is it is long gone.
I will tell you some of the best advice I got when I was in that situation and all of them seemed like they sucked at the time.
The following is what my friends did for me when my ex-wife decided to leave:
My friend John told me, you don't quit a job until you have another job that provides you income. His point was she has moved on, you are the only one stuck here.
My friend Tim at a club, Dude that girl is all over you and you look like a dead fish, you are letting her (the ex) memory make you a shitty date for this girl, who by the way looks much better than she ever did. So you, who have the power over this date is letting her in on your date and ruining it, oh and by the way isn't se banging another guy. He then went on to explain to me that her date was probably doing just fine.
My buddy Joe-Joe who would invite 10 or so girls over for a pool party at our house, every weekend. Who was nice enough to never try and push me, he just knew providing a fun environment, would bring me out of my shell sooner.
But it was finally my buddy Andy that snapped me out of it, by basically showing me, and giving me a tough love talk about the fact that she had moved on.
I wasted months moping and whining over a person that has moved on. In most of these cases, she has moved on, all of these guys seemed like jerks at the time, but they were my real friends, the one really working to free me from the chains that only I was in. This gentlemans best bet is to move on as fast as possible. She is not coming back and the funny part is the only way that she will try to come back is if he moves on.
Alternative is digging into self loathing of how he should have proposed earlier to make it work, etc.
Connect with real mental health people. Not distant randos via text that doesn’t really help biological processes work themselves out.
Everyone has issues, not just from covid.
Someone is always losing a family member or separating.
You may not know it and make all manner of comments.
What Americans need to do really is get over the obvious failures of their culture and redirect their agency to fixing it concretely.
I look forward to screen addicts doing the opposite.
Please, I beg of all of you, do not forget what kindness and compassion can do for all of us, and that no matter where we are now, life and success is fragile and can be taken in an instant. Are we all anti-social corporate robots on here? So much so that the usual 'all business' crowd is now attempting to convert any 'human and not business' threads back into the corporate ethos? Why can't we just say something nice or leave and go back to toxifying about the latest Twitter gaff or apple device. As much as you can say that this forum is about silicon dreams, I can say this forum is equally about the human minds that have them. This forum and more its tone is what we make it, and the recent anti social push worries me and threatens to push any actual compassion away.