Thought in action utilizes energy. All kinds of mental activity require mental energy to be performed. All mental activity, whether it is for creating, analyzing, getting worked up or being jealous requires energy.
Since any activity that involves the mind requires energy it is important that we direct our mind into only towards fruitful and beneficial activities.
Whenever we get angry against someone, get irritated or frustrated we expend a lot of mental energy. When we spend a lot of time just getting worked we will feel exhausted after some time. There will be times where we repeatedly relive some situation and keep getting angrier and angrier. We will dwell on some cyclical thought which will enervate us. The energy that is spent in our irritations, frustrations or anger serves no purpose. This will only make us feel drained of energy.
On the other hand if we spend time directing our thoughts towards fruitful activities then the mental energy that we expend will give us some useful result. For example we could direct our thoughts to solving our immediate problems or in learning some new skill that will help us in our personal or professional life. Alternatively we could focus on planning for our future and taking necessary steps so that our path in the future is smooth.
This is judicious use of our mental energy.
But the problem with most of us is that we fritter away our mental energies in petty disagreements, in hate games, in irritations and anger. We do not realize that this sort of mental activity is a waste of our mental resources and will only makes us feel drained after some time.
If you feel angry about something or someone try to see the futility of it and get rid of it as soon as you can. Do not prolong this feeling. Re-focus your mind on some other useful activity.
Expending energy in wasteful activity like anger, frustration or irritation is equivalent to banging your head against a wall. It serves no useful purpose and we will only tend to feel tired.
So we must learn to avoid any sort of mental activity that serves no useful purpose and direct our mental energies towards creative and problem solving effort.