Leslie Berkowitz is an inherently mournful man, through no fault of his own — he has been treated unkindly by a cruel world, but not as badly as he has been treated by his own family. His professional experience, at least, has some semblance of normalcy, being a practicing doctor with a thriving clinic, but he still doesn't seem to find much joy in it.
His role on relationship with Schneider, however, and they consider each other the father/son they never had. Still, how does one choose the most dismal moments of this character, when nearly everything about him screams sad?
Led On By Lydia
Lydia has never truly gotten over her late husband's death. This shows that their relationship must have been extremely close, as she can't fully let go of Berto after so many years.
However, Leslie clearly cares about her very much, as shown by the way he is always there for her when she asks him to be. And while that shouldn't mean that she has an obligation to like him back, it's still sad that he can't find a relationship to invest in that will bring him joy.
The Whole Deal With Esme
As an extension of the earlier point, he begins dating a woman named Esme when Lydia officially declares that there can never be anything romantic between them.
For some reason, this makes the latter super envious, and, eventually, Leslie then dumps Esme so that his friendship with Lydia remains unaffected, which is most certainly not fair to ask from anyone.
His Ex-Wife & Daughters
Leslie's miserable marriage ends in divorce, but the details of his experience are discouraging at best. He mentions that she left him on Valentine's Day, and to make things worse, asked for a divorce on April Fool's.
If that's not enough, his daughters don't pay attention to his existence unless finances are involved. It's strange that Leslie is completely fine with paying for their homes and marriage ceremonies because they are taking advantage of his niceness.
His Birthday Sorrows
Dr. Berkowitz doesn't quite enjoy the act of celebrating his birthdays, mostly because it only reminds him that he's growing older and frailer.
Further, Penelope mentions that she wants to give him one enjoyable celebration because apparently one year he had visited Medieval Times (the well-known dinner theater production) for his birthday, where he, unfortunately, received a bite from a horse. How he managed to do this is a mystery, but it just adds to the sadness that is Leslie.
Exhausted For The Last 35 Years
Leslie mentions that he has been "exhausted for the last 35 years" when he hears Penelope discussing how studying to be a Nurse Practitioner combined with the rest of her responsibilities were causing her some serious stress.
Though he can't know the hardship Penelope is grappling with, it speaks to his overall state of mind and living. Leslie doesn't seem to be bothered by it, really, but this fact about him is quite lamentable. Hopefully, he learns about the importance of rest soon; he is a doctor, after all.
Once Wanted To Be A Singer
Leslie mournfully exclaims that his dream was to be a singer, a career he wasn't cut out for. Still, it's not fair that he never got to achieve his ambitions, as being a doctor clearly isn't doing anything to better his mental or physical health.
Perhaps this is the reason he enjoys going to the opera so much, to vicariously experience a profession that could have been his in another world. It's not known if he can actually sing, though, so there's that.
Can't Stand Up For Himself
Leslie basically deflates when exposed to confrontation, because his natural tendencies tell him to run and hide in his shell and hope the source of conflict dissipates by itself.
Forget the notion that avoidance is a terrible way to go through life, it's certainly not doing him any favors to bow and scrape before those who manipulate him. For once, it would be nice to watch him take charge of the situation and make it clear that he will not be trampled on anymore.
A Morose State of Mind
Leslie once says, "depressing is my default" which speaks volumes about his state of mind.
It's sad to see him feel so down about himself and about his life, and viewers can only hope things brighten for him at some point.
Doesn't Know Where To Begin When Dating
In order to ask Lydia out, Leslie pretends that he's explaining how his office works to Alex (who happens to be working there). He tells him to act as his grandmother, then goes on to raise all sorts of bizarre queries about her that have no place being in a patient history file.
Alex catches on pretty quickly and gives Leslie some advice on how to impress Lydia. It seems a little unethical to be trying to gain insight into Lydia through his profession, but it's hard for viewers not to empathize with the idea that Leslie needs a lot of help figuring out how to break the ice with the woman he likes.