Situation: I hang out with A for a while. Having lunch together, shopping for a bit. I now feel tired and I want to go home. I don't dislike the person and I don't want to give them the impression I do, but I can't enjoy hanging out with them when I'm tired and I'm not enjoyable to hang out with when I'm tired, so there isn't any value for either of us to continue at that time.
Note that I mean tired in general, not just something that would require me to rest my legs for a bit, but rather the kind of thing where I lock myself in my apartment and don't come out for the rest of the day.
I'm having trouble telling A that I would like to disengage - stating it as a matter of fact "I'd like to go home now" doesn't work (they want to know why). Telling them I'm tired doesn't work (they don't understand that I don't just need a rest in a café or something along those lines). Making up an excuse doesn't work (I don't like to lie and I'm not good at it anyway).
What is a good way to go about this?
(Different situation, but the same thing happens when I have prior occupations like "I plan to do laundry later today", I can't communicate to people that doing these things takes time and I wasn't expecting our meeting to last all day when we met up).