I agree with putting the key away until you can copy the speed you wish. The reason is most people can send faster than they can receive. But ... inherent in that is, if you are sending faster than you can copy, how do you know you are sending correctly?! You can't copy it! So you start to learn "bad sounds," that are not correct code, as you are listening to yourself. But once you can copy good code at 15-20 wpm, it is very easy to learn to match your sending to that sound.
Machine-sent code is best to listen to, of course, and W1AW code practice and bulletins are terrific, and include the extra benefit of teaching you to use your 'head filter' to sort out the various signals that are trying to interfere. The G4FON software is excellent, really, one of the best, for you tailor it to your specific needs of the moment.
Comparing code to a language is probably fair. I lived in France for three years and learned French very well. Yet two years after I left there I was losing that ability and I wondered why. I met a French lady who had lived in the US for 12 years at the time. She could no longer speak French! That amazed me! But it also told me the "use it or lose it" adage is true. I felt less bad about my own loss of the language.
Similarly, I used CW professionally, at speeds in the 20-35 wpm range, for several years. And since it was code groups, there was no such thing as guessing. It had to be letter perfect. Yet, when I wandered away from code use (after leaving that job) and later returned, I found my skills were more in the 15-18 wpm range max, not even up to my license testing! Since then I have tried to keep 'solid copy' skills around 20 wpm, and as I get older that gets harder! 'Mental copy' skills remain around 35 wpm, but on a bad mental day I may drop to 20 maximum. Use it or lose it, indeed. I can't compare it to a bicycle, but then again, I haven't tried to ride one of those things in 10 years or so!
Have fun, enjoy the code, at whatever level. I wander the Novice bands (40, usually) and if you hear me on, give me a call. Would love to work you.
Ed