Only caveat to this is I find if the last practice before a gig goes too well then the gig isn't so good for some reason. Conversely, if I have a fractious, difficult practice before a gig, the gig goes well!
I know what you mean though, last week I idly started playing "Unsquare Dance" (7/4 time), keyboard player picked up on it and after a couple of abortive attempts the drummer got into the 7/4 thing and it was great, really enjoyed it. Want to do it again tonight