There are 2 types of tiredness – either the body is tired or the mind is tired. If the body is tired, you need to rest your body. If the mind is tired, it’s because of defilements.
If the mind is tired, you need to meditate. When you meditate, good quality of mind comes and the bad quality of mind reduces – that means the mind becomes more relaxed, peaceful, open and less tired.
First, you need to think of the tiredness as an object. Don’t try to push. If you push, that’s another defilement too.
Mental fatigue is because of defilement – sometimes craving or aversion is strong. When any defilement becomes stronger and stronger, the mind becomes tired.
If the awareness, stability of mind and wisdom are growing, the mind never gets tired – it becomes more peaceful, tranquil, equanimous because of meditation.
If you practice and the mind becomes tired, and increasingly tense, then something is wrong with the meditation. Then, you should check how you’re practicing, what state of mind you’re meditating with.
If you practice in the right way, the mind becomes more and more relaxed.