Ideas Are Easy.
Yes, they are. Whenever I tell people that I write books, they say "Oh! Yes! I have an idea for a book, I'm a writer too!"
Writing Is Hard!
Yes, yes it is. If all you have is an idea, then sooner or later, you'll run out of steam. You need a good plot, characters, show vs. tell, etc. etc. etc... so many things to remember about craft.
Writing Is Work! Yes, it is.
If you're not prepared to make sacrifices to get the work done ... it's fine. You can be a hobbyist writer, and that's fine.
Rejection ... oh yes. Yes, yes, yes.
Best way to deal with it? Don't Give Up.
Finally ... Well ... Not Enough Money in it. That's always a possibility. (Unless you become a lucky unicorn!)
Like any other industry, getting success - finding an agent, a publisher, an editor, whatever
- is a long, hard slog. Good things come to people who do their work and are prepared to wait, and some novice writers just don't understand that or aren't prepared to deal with it, and so they just throw their hands in the air and say "Whatever! You people don't understand my genius! I'm gonna go to the living room and watch TV!"
Well.... good luck to you, then.