It appears that the issue here is: do I consider an aveira, or more honestly: "a behavior that is bad for me", to be a breach of bottom-line sobriety? This is a question that, in my opinion, is judged by a program and between an addict and his sponsor. There is no sobriety definition in the Torah, as the Torah is about goodness and holiness, while any 12-step program in the AA tradition is about derech eretz: sanity and health (a recovering addict can then start from there towards whatever religious goals he/she may have).
If your sponsor is this website, well, I can't speak to that at all because it was not my experience. For me, if determining my sobriety definition/date were purely my decision then I run the risk of being the judge of my own sobriety - ie, what's not OK. The next step for me would likely be deciding what is OK and the next step would likely be whose wife is OK...I am dead seriousl. I stick w/SA's definition because I choose to be a member of SA, where I found sobriety. As far as playing with lust, my sponsor and I just figure: if I "play" with it I am guaranteed to act out soon anyway - then there will be no question as to whether my date needs to be changed. Sad but true. BTW, if you are not an addict, but just have some trouble with lusting, none of this applies to you, for your basic concern is goodness vs. aveiras. Is this clear? Useful?