[herbst]

Did you try l-theanin? That is contained in green tea and arguably one of the reasons you don't get caffeine rushes and withdrawals from excessive tea use.

I use it mostly against anxiety I can get from high caffeine intake.

On the other hand dextroamphetamine works just long enough for an average work day and has much fewer crash symptoms than other common amphetamines. I wouldn't recommend abusing it for work tho, that's a downward spiral IMO.