What Mike said. Every team is different as opponents, and respond differently to your tactics. Adding to that, your own team may have an "off day", especially if they're not focused and concentrated (can happen when beeing big favourites).
In pre-match talk, tell them you expect a win. That way it is easier to be strict in mid-match talk and afterwards (if you first tell them "good luck" and are angry with them afterwards for not winning, they'll get confused and angry, of course)
When beeing huge favourites, I would go for a controlling/posession strategy (which of course I have trained for a long time, so that my players are comfortable in that formation/tactic). Nevertheless, I pause every game after 8-10 minutes, to see if my ***. manager has picked up on something vital. Maybe we should play shorter passes today, ease up on the tackling, etc. (your ***. manager should have pretty good tactical knowledge stats for this to work). The earlier you start fine-tuning according to game development, the better chance of a good result. (no use in analyzing after two minutes, though)
I try to stick with my strategy (with just some tweaking), unless I'm down by two goals or my ***. manager tells me everything is wrong. I find that changing tactics too much during a match makes the players confused and unhappy. If your tactics doesen't really work, but you are still keeping a clean sheet, stick with it for 45 mins. In the break you change whatever is needed, and tell them they're not performing as expected (if they are not). This usually brings out the best in them, unless morale is very low (then they need encouragement like "I have faith in you"-stuff).
Anyway, this usually works for me, hope it does for you.