Even if someone wants to do something for you, how do you know that in doing so they're not self-sacrificing and wearing themselves down?

For example, I (24F, single, childfree) can't see the downside to being provided for in a relationship - or even while dating - but I don't understand how this can result in an equal energy exchange. Something doesn't come from nothing, and energy can't be created - only exchanged/transferred.

I'm ambivalent about being provided for because I don't want anyone to self-sacrifice for my sake. Nevertheless, I would love to relax while someone provided for me.

Can you please help me understand the theory?