Positives in the medical fields are most of the time BAD. But Positives in writing... That's good. Look people and I mean this because I've experienced it. Every writer has. People will try to break you. They will try to worm their way into your head and tell you how, Terrible your characters are. They'll tell you well so and so has a book just like this. They'll say well, you aren't going to make any money unless this becomes a movie.
These people might be those you'd thought would support you the most. They might have been your BFF, your mother, father, sister, whoever. Point is they'll say it's because they think this is a brutal business and they're only looking out for you. Maybe they are. Maybe this is them caring. But listen, they're also crushing your dreams.
If you think you can hack the rejection, or the waiting, the trolls trying to put you into a dismal place then stay positive. Stay focused on your goal and go for it. The worse that can happen, you try and fail. I failed a lot before my book got picked up. Seriously. my first book ever is some printed MS somewhere in a box. The computer that had that file crashed and burned. Second book no better. It's resting in a pile of awful attempts. Third, fourth ... My sixth book, finished novel is with a publisher. My fifth I self-pubbed. Point, I never gave up. I stayed positive and focused on the task. My seventh is a short story and is getting pubbed in an Anthology.
So it might take you five tries. Might take you two. Might even be 20. Just be positive, keep working and you'll get there.