I'll try to keep this brief since it could turn into quite a long story.
The gist of it: I (late 20s) live with my closest friend (let's call him Ben), and for the past decade, have always worked out together and motivated each other in a variety of competitive sports.
We both come from a non-running background (rowing), but both started running after getting into triathlons, and for a good couple years enjoyed going on runs and other workouts together.
Having lived together for the past few years, this made it convenient to enter/compete in many of the same events, from Tris to a handful of road races (5km/10km, HM, etc) for the fun of it. It's also made for a very convenient training partner, someone to motivate you to get out the door or get that run in even when you were feeling lazy.
We've both seen very significant improvement in our abilities, but in many cases when it comes to results, I've always remained a half-step ahead in many of the competitions.
Over the past 12 months or so, the nature of the relationship is degrading significantly, and I think a large part of it is due to the competitive nature of Ben and I. We've known each other for over a decade and have always had strong alignment in our athletic interests. This has led to a constant but informal battle of one-upping each other, whether it is in speed, commitment, investment, or volume, we are always aware of what the other is doing.
Lately however, Ben has been more focused on doing his own training, and has started avoiding our working out together almost entirely. He's told me that not being able to "beat me" in whatever event (or training session) has completely ruined the joy of both training and racing for him almost entirely, to the extent he doesn't want to enter any event I'm also interested in. He says he feels horrible regardless of how hard he works, as long as I am in the picture, it diminishes his effort and sense of self achievement.
He has admitted that his mindset is not a healthy one, but one that is unavoidable for him. He's even brought our work into the argument, saying the differences in performance can be attributed to him having a more difficult job than I do. As a result, we are now reluctant to work out together entirely, or even talk about training anymore.
The working from home and quarantine situation has compounded this effect, giving me both more time to train, but less (zero) opportunities to just go meet other people to train with.
Even more recently the pettiness has reached new levels, as I know he obsesses over my strava data and will make passive aggressive comments about the workouts we didn't even do together. I feel this is driving a major thorn into the friendship and one that won't necessarily heal on its own.
If there were a "harden the f up" pill I could prescribe, I'd just do that, because honestly, I've never seen another adult take on this particular attitude, but since there is not, I'd like to ask for suggestions on what to do to help fix things.