Upvoted for being one comment.

I wish there were psychologist/therapist gift vouchers for frenemies or people you have to stay in contact with for a long time due to work or familial obligation...

Sure, it's called The Fountainhead, and it's for you. (That is, your obligation to maintain contact with your family is entirely voluntary.)

But more helpfully there are lots of therapy / self-help books that are full of useful skills that you can sometimes improve a relationship by giving to the other person. This is typically recommended against because a very important variable in the success of interventions is 'therapeutic alliance'--if someone isn't interested in a book, they won't read it, and if someone doesn't want to work with a therapist, they'll sabotage the experience.

It is worth focusing on how you can adjust your behaviors around the difficult people in your life, and this is something that you might want to bring up with a therapist / get books to look into yourself. (When I was dating someone who was anxious, I read self-help books on anxiety, for example.)

Is that attributable to global variation in sentiment of lesswrong voters or to temporal variation in the karma attrativeness of my posts?

Pretty sure it's the latter, but in a moving average sort of way--a bad comment not only is likely to be downvoted itself, but also makes it more likely that other comments posted at around the same time are viewed as bad.