For me, the combination of best and worst came from John Jarnold, some years ago. Due to an unexpected windfall I could afford to have my only full-length work edited by him. He didn't provide a line edit as I 'had the basics pretty much down pat', but pointed out the usual pitfalls of new authors; too many ideas leading to extraneous sub-plots, clever rather than realistic dialogue exchanges, etc. - all of which I've (hopefully) taken on-board.
But...
He also included an overview of the publishing environment and its brutal realities - presumably as a 'forewarned is forearmed' approach to submission/rejection. However, in passing he mentioned it had taken Iain (M) Banks sixteen years to get his first novel published, and that just killed it for me. I was in my early 50s then, and simply didn't have the time, energy or inclination to join the churn cycle. Hence I don't really 'market' my work, merely release it via those outlets that will have me, and that's enough.