I had just started using svn for 6 months when I started using git.
Let's say I was lucky that git has the same logic as I.
For me, doing something in git is (relatively) easy, as long as you know what is your current state and what final state you want to get.
I still have problems with some behaviours that are illogical to me, like submodules.

Back to mercurial.
At work, I had to migrate from using git to hg around 2012–2013.
hg was so much confusing to me.
It was always in the way of how I used version control and I had to add a plugin or something to regain some control on my local repo, to edit commits and local history as I see fit.
I still don't understand what is gained to hardlink a commit to a branch.
Why can a branch have more than one tip?
It was very enabling for my collegue that never did a merge an just push his work as a new tip.
You can't be that lazy on git. Or you can try and others will easily see that you "forget" to merge your working branch (or push -f 🤬).

Let's just say I went happily back to git after that and let time not using hg erase what I had to learn of it.