I have lunch with a mandarin speaker once a week to practice. My parents native tongue is cantonese, so it's similar in grammar at least to mandarin. I found I really suck at speaking cantonese, but a couple of months ago I went to China. With no english speakers around me, I was forced to adapt, within 3 days I was speaking fluent cantonese to my cousins. So I'm a firm believer in practice makes perfect.