The question has come up, "what to do when your partner misses the easy ball?" And we could intensify that to "what to do when partner misses three in a row?"
I've played a lot of bridge, a sport where the partnership is everything. Bridge divorces happen and it's probably a reasonable idea not to play with your real spouse! (That's not quite correct, but I'm exaggerating a bit here.)
PB is a silly game and to get upset about a partner who misses a few shots is a path to madness. Why? Because you are probably going to miss three in a row in the near future. How do you want your partner to react?
Besides the play, every game is a chance to enjoy the synergy of a partnership. There is a lot of individual effort in life, but here is a chance to work with someone to achieve something together. This is a great thing. A nice shot to setup partner's put away is a rewarding achievement.
Now let's flip this a bit. It's easy when it all goes well, but not a lot of fun when nothing seems to work. First case is partner screws up. To lessen the chance of that happening again, you want to support partner, encourage them, concentrate on the next shot. As my grandmother used to say, "No sense dwelling on the past." Of course she had little short term memory, so she couldn't dwell on the past, but that doesn't make her wrong. Bottom line, help your partner! And being critical is rarely helpful. I think beginners are interested in help and if it's something basic, talk to them after the game.
And what if you err? You try the stroke again, you are not happy with the miss. If you've missed a couple before, you question your choice of hobby and wish for a quiet place to recollect. If your partner is not supportive, it makes it worse. You've already chastised yourself, you don't need partner to pile on.
Bottom line in all of this is to work to make your partner have the best game you can. It might not be a win, but there ought to be the satisfaction of working to a common goal and hopefully spending a fun ten minutes together.
There is one more situation that occurs and that is your team is out classed by the other side. Maybe the good players wanted to get a game together instead of being split up and you should encourage that on occasion as you get a chance to see two players moving about the court properly. Ok, you don't expect to win, but here is a chance to bond together and do the best you can. Think of it as a learning experience and don't worry about the result. You might find that you put up a better fight than you expected and at some point realize that you might actually win the game. Good times then...
The final point I will make is that the difference between a good shot and a poor one is very small. A great dink and a netted ball is measured in millimeters. This is a simple game that you can't be perfect while playing. There are bad bounces, strange skips, opponents who work miracles and partners who turn you into a pin cushion. You cannot expect to be perfect or always be rewarded for a good shot. All you can do is try to make a good shot and then... move to position to defend the next ball. This is true for all levels of play. I've seen video of Ben Johns miss the simplest shot twice in a row. Of course a soft touch shot is not really simple, but he didn't expect to miss either much less both. We will all miss simple shots, so no excuses, just take a breath and get ready for the next chance to play well.