I have been generally successful at learning Russian as an adult, but tonal languages are something that I just struggle with on a fundamental level. I want to express meaning and connotation with tones, rather than denotation. On the other hand I've never been terribly motivated to learn a tonal language, so it probably could be overcome, but it's something that would take an immense amount of training to overwrite that tone=connotation/emotion/question instinct.

It is also quite frustrating when a native speaker is completely unable to understand something you say because of a tonal issue. To their ear it must sound entirely different, yet to a non-tonal ear it sounds like you're saying everything 'almost' exactly correct.

Right but those Mandarin tones are pretty easy for an native english speaker to learn to say, they roll off the mouth easily.

Likewise, learning to speak the tone is just another grammar dimension, memorization.

Listening for tone is the hard part, but once you know enough grammar AND know the context of the sentence, it falls into place.

YMMV, also Cantonese is more difficult here (IMO).