That is true....but, spitting on Christ is also a grave sin.
Perhaps there are some underlying and unresolved issues that brought this about.
You could have just as easily shattered a lamp or ripped your clothes to shreds....but, you chose to take out your frustration on Christ and His saints. You actually tore off your baptismal Cross.
To me, this seems more than a temporary loss of control....but, an unresolved situation simmering just below the surface.
However, remember James, all sins are forgivable, if the person repents. Therein, lies the gravest of issues...the fact that you feel no remorse. That needs more inspection on your part.
Praying you find peace of mind.