Martin Fowler has put up a thoughtful insight.
The point is that when you try a new technique it’ll often make you worse, at least initially. You have to work with something unfamiliar, perhaps also unlearn something else that gets in the way. During that period you performance has dipped. Only with perseverance can you get through this and reach a higher plateau.
To improve you might have to try something new, and something new might be uncomfortable which will put you down in the pits. Temptations of the comfortable zone can stop you from trying, fears of not gaining a higher ground can stop you from trying, but trying new things and evolving is the way to improvement.
I think this applies in all the fields, more so in software development where you have to keep learning but still face who don’t. Well, if you ask why improve, the first line says it all.
If you care about what you do, you care about getting better at it.