its all about correct upgrade choice and learning boss patterns...after some practice becomes very easy...and as for the canon happy...this is straight from the guide..."This achievement is difficult, but not as much so as it may seem. You must complete any 11 levels of the single-player campaign (in a single playthrough) without dying or using a nuke. You are however allowed continues. If you die during a mission, allow yourself to be killed 2 more times quickly and start the mission over. It is advised that you do this on the first 11 missions, as each mission is harder than the last."
Hope that helps.
Now We Must All Fear Evil Men, But There Is Another Kind Of Evil Which We Must Fear Most, And That Is The Indifference Of Good Men.