If you have to keep telling yourself the same thing over and over again, there is a good chance you don't really believe it yourself.
I don’t have to, but I have to try, at least, from letting you muddy the waters.
To recap:
The reason for secession was the South’s desire to preserve slavery.
The trigger for secession was the election of Abraham Lincoln, which fed fear of the abolitionist foundation of the Republican Party.
The American Civil War began when units of the South Carolina Militia fired upon a Union fort in Charleston harbor.