Never take Tea/ Coffee while your trading or before trading. Yes you are right no tea no coffee in trading hours. why?
Every thing I am telling you has a scientific reason. Taking these beverages increases your heart beat rate. Your increased heart beat rate requires more oxygen to burn for its increased rate, as a reason the oxygen which was supposed to go towards your brain (mainly frontal lobe, used for decision making) ,gets disrupted.
This low oxygen supply to brain results in the state of doubtfulness and indecisive state of mind and hence results in entering in wrong trade or not able to think properly, while you are in the trade.
Hope you are able to able to link it some of your past experiences. Our Broker Friends don’t know this and they serve clients with 2 or 3 times tea or coffee while trading hours. You can replace tea with some other healthy thing like nuts, peanuts, Jamun, or other small time pass healthy fruits that don’t affect the trading decisions adversely