I studied Latin and Ancient Greek at school and university - to a very high level.
They are reputedly hard languages: very different scheme of grammar from English, and an alien script for Greek. In terms of the workload, at any rate, they constitute almost certainly the most demanding Arts subject* at Oxford... and one of the most physically demanding sets of exams in the world (11 or 12 three-hour papers in a little over a week, for both the mid-point and final classification in the undergraduate degree; it was commonly said that only the entrance test for the Japanese Civil Service was more gruelling).
In short, I think my brain is full; or more properly - since I have, to be honest, forgotten nearly all of the Latin and Greek I used to know - worn out by that exceptional language-learning effort in my younger days.
Even more to the point, Latin and Greek are dead languages. Nobody speaks them any more, and, in learning them, little or no attention is paid to speaking them aloud or attempting to use them as a medium of daily communication. (Some folks have experimented with 'communicative method' teaching, attempting to develop skills in these languages by adopting the same language teaching methodologies used for modern languages. That approach, though, was pretty much unheard of in my day, and is still, I think, a bit of an eccentric minority interest.)
And I was quite happy with that. I learned these languages with a focus on the literature. I was thrilled about the prospect of being able to read great authors like Horace and Homer and Tacitus and Thucydides in their original language. It seemed a much more worthwhile objective than being able to mount a fumbling conversation with a shopkeeper on a summer holiday in France - which was about all the modern linguists at my school ever seemed to achieve.
I liked French, and pursued that to quite a high level too. I did a supplementary literature-based exam in it (on Voltaire's Candide) when I was 15, and continued studying in my own time during my 6th Form days - reading quite big chunks of Balzac, Maupassant, and Zola (more, probably, than most of the French specialists among my contemporaries), and trying to force myself to watch my favourite French films without referring to the English subtitles. Trouble was, my focus was solely on the literature. I never went to France for a holiday as a kid; and when I finally visited for the first time as an undergraduate, I found myself embarrassingly tongue-tied. I had liked to think I could maybe have discussed Flaubert or Baudelaire with someone, but in practice I could scarcely buy a baguette.
I'm afraid my interest in Chinese is much the same. I'd love to be able to read Chinese, particularly some of the classical literature: the Analects of Confucius and the great poets of the Tang and Song dynasties. But that damned writing system is just too much of a barrier to entry. I know I haven't got a hope in hell of cracking it, coming to the study in my weary middle years, and when I have so many other interests and distractions in my life.
You don't really need the language to buy a baguette - or a mantou.
[* I suppose Chinese is probably even harder. But in my undergraduate days, nobody really paid it much attention. I'd guess there were probably only a few dozen people in the whole of the UK studying it back then.]