I saw two very wise quotes about the film business by director Gina Prince-Bythewood ("The Old Guard"):
"This industry is about overcoming 'no'."
That's true of the publishing industry as well, and probably all of the arts.
"You need just one yes."
Actually, sometimes you need more than one, but one gets the ball rolling.
Yes, it's a bit like looking for a needle in a haystack, and that's how the people on the other side see it, too.
Producers are looking for something they consider special and often they don't know it until they see it. They see a lot of scripts that aren't it, and finally one that IS it.
Sometimes--no, MOST times--your script isn't it. But they're going to keep looking so if you keep writing good scripts and submitting them, it may well be that one of those times it is a match.
If you remember that 'no' is the rule rather than the exception, the process gets a little easier to bear. But Prince-Bythewood says, "But it's hard. There were many days where I was on the floor."
I got to know the floor, too, and sometimes I still find myself on it. If you can deal with that, you're on your way.