Bodily and mentally, relax; so any time you’re finding yourself tired, rest. Don’t do anything to make yourself tired from meditating. But be careful of becoming dull and tired.
You can get tired from also not putting in enough effort; like it’s more tiring to sit than to be working sometimes. If you’re sitting for hours, that can be more tiring than running.
In that sense, if you notice you’re becoming tired, it could also be because there is not enough energy.
So, it needs to be relaxed but interested so that there’s energy and that keeps us alert.
And this energy that is interest, that’s a function of wisdom. Wisdom is also our common sense, our curiosity; all that is wisdom at work.