You are not deluded! You are cautiously optimistic.
Everyone thinks that they can write a book. Funny, because not everyone thinks that they can paint a masterpiece, or play the grand piano, but if you talk to 10 people probably 8 or 9 of them will say they're writing a book or they thought about writing a book or they have a friend who has been writing and they've been thinking about writing one themselves, or they wrote one 20 years ago but they didn't get round to getting it finished published blah blah blah blah.
But that's not you. You are writing your book. You are planning how you want to continue writing. You are seeking and acting on advice, and have some good support by the sound of it, on your course.
Getting your book published is the first hurdle (after writing it, of course). But that's followed by a series of other hurdles.
The world of publishing is like a crowded, shallow, seething pool, full of sharks, with some amorphous semi-opaque things that lurk in the dark corners (some of which are parasitic organisms, and some of which fell into the pool by accident and don't know how to escape).
Sometimes it seems that it's impossible to find an agent and then get a publisher. But we know it's not impossible. It's hard though, and disheartening because there are so many mediocre/ shite books out there that have done ok, thank you very much. There are also the occasional authors who don't have an agent, but get a bargain publishing deal (not much upfront money) then hundreds of people buy their book and the agents come rushing to snap the author up. Very rare indeed, that.
I don't think it is possible to be quite prepared for what happens after you get a book deal. It's a bit like when you get married or move house or have a baby, you imagine what it will be like and it absolutely never turns out like that, for a myriad of reasons.
But that is not a reason not to do it. You're a writer, you have to write. Hone your craft, and all that.
Finding the way that works for you is an excellent start. I know you can do it, Lurky ... and BabyOrca and Myrtle too. Keep on writing. And if you want anyone to read your books let me know (for a very reasonable fee) 😁