Well, other people are doing stuff about rejection (Lucy for one).
Most advice boils down to "it's not personal" and "it does not reflect on your skill". Which is right.
I thought I'd mention that at one time I was on the other side of the fence, though in a slightly different area: I was an editor of computer magazines in the 80s and 90s. There was a time when we would get contributions of articles and computer programs (these were the days of "type-it-in-yourself" computers).
There was a percentage, about 90%, which were rubbish, most of the other 10% fitted into the "we've already got or had one of those", some were effectively replacements for regular columnists so could not be allowed, and maybe 1% were usable. And of those most needed re-writing, either for style or English. Sometimes we rejected because their programs, even though they worked, were so badly coded they would be bad examples.
So we had a standard rejection letter with the most common reasons for rejection listed with tick boxes, a space for the name and the article. And we would spend time each week going through the submissions, reading them, testing the programs and sending back the rejections.
We did not care who the people were, and we appreciated the fact that they wanted to contribute but we couldn't take them all, even if they were good enough. Every industry has its financial constraints, many people thought we could just "add pages" to make the magazine bigger to fit their articles and programs in. (It really doesn't work like that.)
Yes it's true that every now and then something would come through that was so appalling we would make jokes about it. Sometimes there would be the arrogant bar stewards who thought they were god's gift and we owed it to them to use their work. In those instances, where we could tell, we would reject because their attitude implied future trouble, no matter how good they were. But they were few and far between.
So we sent out our standard rejection letters, we never ignored people (unless they forgot to put in their address, it happened). I'm sure some of them took it personally, but how could it be personal? We didn't know them, the judgement was based purely on whether the submission was something we could use or not; and even if was brilliantly written it still had to be appropriate for the magazine.
As an aside, my wife was also a magazine editor at that time (we worked closely for 13 years while married, and loved every moment of it - we only ever had one domestic in the office, it was amusing watching people backing away). Anyway: She launched a new magazine intended to educate parents about computers with respect to children. It was announced in Writers Magazine with a very clear statement of intended content, which did not include stories (it was a techie/education magazine at the end of the day). Yet she received handwritten stories about cute little pussy cats and whatnot. Unsurprisingly they were rejected - one of those rejected authors actually complained. (Living in the real world, not.)
I made some great friends during that time from the submissions we did accept and people who wrote for us regularly, and by a strange quirk of fate one of those people is also a finalist in the Red Planet Competition: William Gallagher. If he wins, I taught him everything he knows. If he doesn't, he wasn't listening. (For the avoidance of all doubt, the preceding sentence is a joke.)
So that's what it's like on the other side of the rejection fence. It's just business.
What's on the turntable? "Ricochet" by David Bowie from "Let's Dance".