I tried to substitute tea for coffee a while back because the coffee I was drinking was giving me really bad anxiety in the mornings, but the higher caffeine teas were honestly just as bad or worse, and the tannin content would have me all jittery. I think I’m particularly sensitive to tannins, though. I couldn’t really ever find a tea that was a good balance between enough caffeine and low tannin content, while switching from a blonde roast to dark roast pretty much solved my issues with coffee…