This is basically meditation and I find it very helpful. A cool trick I like is visualizing my thoughts as clouds that spontaneously emerge and pass, letting them disappear forever without remembering what they were, to give place to the blue sky that is the calm mind behind. That is, while you are counting, if a thought emerges, turn it into a cloud and let it evaporate.

I found guided meditation apps like (headspace in particular) nice to get the setup.