One Thing Bothering Me

Great win and I can't wait for the game against KC.
One thing that is really bothering me, and has always bothered me in the Tomlin era.
Why is it that our team always has the attitude that we will do the minimum to win/or get the lead and then put it on cruise control and just hope we coast to the finish line ahead of the opponent?
It's like a prize fighter that hurts his opponent, and instead of going for the knockout and finishing the win, just backs off and hopes the opponent throws in the towel and doesn't rally back in throw a knockout punch of their own.
Where is the killer instinct of this team? Where is the heart to play 60 solid minutes, without the constant lapses, that have come back to bite us so many times?
Spurts of great play always followed by maddening lethargy as we rope-a-dope our way to a split decision, hoping we don't break a sweat or get sucker punched. .
Gawd, smell the blood and make the ref pull you off the limp challenger laying unconscious on the mat!
How many times are we going to have this attitude and let good playoff teams beat us, or come from behind on the cards and take the win.
I get that the game ebbs and flows, but we keep shutting it down inappropriately.
Yesterday we totally dominated, then shut it down before half time. Miami never really threatened us seriously after that, but, we completely gave them the opportunities to come back and win it, if they had been a better team.
This scares me with both KC and The Cheatriots up next (in their own cribs no less) in our path.
Tons of talent and no heart is a potential disaster waiting for us this post season that I can't get out of the back of my mind.