I came here to say this. Coffee makes me very anxious and makes it hard for me to focus on tasks. I throw in some L-theanine and suddenly everything is ok. Using drugstore capsules makes it really cheap too.
"These results replicate previous evidence which suggests that L-theanine and caffeine in combination are beneficial for improving performance on cognitively demanding tasks." https://pubmed.ncbi.nlm.nih.gov/18681988/
"These results replicate previous evidence which suggests that L-theanine and caffeine in combination are beneficial for improving performance on cognitively demanding tasks." https://pubmed.ncbi.nlm.nih.gov/18681988/