You don’t need to explain why you’re tired to people who’ve never carried what you carry.

Explaining a load to somebody with no reference point for it usually produces either disbelief or advice, and both cost you more energy than the explanation was worth. That does not make them bad people. They simply have no way to picture what your week contains. You are allowed to decline the conversation rather than build the whole context from scratch every time.

Have a short answer ready and use it without embarrassment. Busy week, long shifts, a lot on at home. Save the full account for the few people who already understand enough that it does not need building.