Unbeaten in the AIB League since December, the light Blues are now just 80 minutes away from claiming back-to-back league titles.
But ahead of the final against Cork Constitution, O'Sullivan was not allowing himself or his players to get carried away with their four-try dismissal of Shannon.
"It was a two-half game in that we played with the elements in the first half and we really had to work in the second half to beat Shannon back," he said in the aftermath of the Coonagh encounter.
"We couldn't go into the second half without thinking about retaining possession, not conceding penalties and being very aggressive in the tackle to make sure that they couldn't come at us the way we had done to them in the first half."
Backed by a considerable wind, Garryowen barged their way into a 14-3 lead prior to the break, with replacement flanker David Sherry lurching over for a try after three well-struck penalties from full-back Conor Kilroy.
"For us to have that lead at half-time, Shannon were kinda chasing the game. Instead of them kicking away possession, I think they tried to run it too much rather than pin us down in the corners which is probably the usual way that Shannon would play," O'Sullivan added.
"Our forwards really stuck in and worked really hard in the contact situations where we won that part of the game, which put them on the back foot."
Despite the comprehensive win, the former club captain was coy on Garryowen's chances of beating tabler toppers Con next Sunday at Musgrave Park.
"It's a rematch of last year's final, there'll be nothing spared or nothing lost in preparation for this game."