Why do you feel stressed for no reason?Life is stress there is no doubt in it. Often, we get tired because of the mental stress not due to physical fatigue. You are busy but not productive that's mostly because you are preoccupied with unwanted thoughts. Our mind is the source of energy and when our mind is filled with the negative energy then our mind works against us. So it's better to control our mind and apply it in the constructive work rather than negative things. We don't have a control over the results but we can control our actions for sure. Then why can't we do that and have a relaxed life?
Work-related stress also can be reduced by applying few things like take proper sleep, finish your work at the scheduled time and don't wait for the deadlines, make friends and have a chat with them regularly, short walks relax muscles as well as refresh mind, time management etc. These all will definitely help to minimise stress.
Above all train your mind to handle the stress.