Scenes should get better with the rewrites. Muddle through the rewrites till ("until" if you prefer) the end, and whatever happens, so be it. If you worry too much about making mistakes, your writing might become wooden (like this sentence). It's okay to worry a lot about mistakes--that's what rewrites are for--but don't let fear of making mistakes, of writing bad scenes, drain the life out of your writing. (Better the reader think your story was written by a chimp than by a clunky sci-fi robot missing a few critical vacuum tubes--okay, so we're talking OLD Sci-fi robot.)

Have a premise, plunge your main character(s) into big trouble at or near the very beginning (the hook), then do your best to tell the biggest whopper ... prove premise with climactic scene, quick resolution, fade out, the end.

Steve Wheelock