Funnily enough, I've had better results since I stopped doing any active SEO. I used to put in time every day creating links, babbling on social media, commenting, posting and all that stuff. Then one day I got fed up with not seeing much difference and stopped: instead, I concentrated on enjoying my sites, producing content or posting stuff and thinking "forget SEO, can't be bothered".
Almost all my sites shot up by two page ranks, traffic suddenly became regular (and improved) and ad revenue went up.
Maybe it was just a coincidence but I'm pretty happy and I haven't bothered with any SEO since!