The person sharing your day needs to know when you have no attention left to offer well.

Attention is not always available, and pretending otherwise is what does the damage. Somebody talks to you at the end of a long day, you make the right noises while taking in none of it, and they leave feeling unheard without understanding why. Saying you have nothing left right now is kinder than a poor imitation of listening. It also lets them choose to wait for a better hour.

When you are empty, say so plainly and offer a specific time instead. Then keep that appointment, so the honesty is trusted the next time you need it.