It's definitely a challenge to discard your old mental models if/when they start to become hindrances, but far from impossible.
I think this is actually the most important skill one develops by constantly reading up and playing with new technologies and languages. Just as mathematics is as much about learning to reason about things as it is about the particular theorems you prove, learning about technologies and languages and ideas is constant exercise for your brain to absorb new models and reconcile them with ones it has already internalized. Discarding old ones isn't a big deal, because you've been doing that almost continuously anyway. But, like everything else in this discussion, it requires a certain amount of willpower and ability not to take one's own comfortable position for granted.
I think this is actually the most important skill one develops by constantly reading up and playing with new technologies and languages. Just as mathematics is as much about learning to reason about things as it is about the particular theorems you prove, learning about technologies and languages and ideas is constant exercise for your brain to absorb new models and reconcile them with ones it has already internalized. Discarding old ones isn't a big deal, because you've been doing that almost continuously anyway. But, like everything else in this discussion, it requires a certain amount of willpower and ability not to take one's own comfortable position for granted.