That's something I struggle with. This topic isn't about my relationship but it does happen where we have our bad days and end up not being in contact for a few days. But not expecting anything in return is definitely one thing a lot of people struggle with, and something I over-think at times too. Calling after 3-4 days sounds about right and pretty sensible.
(NEW TAWPIC TAIME)
I agree it is something which doesn't come naturally. But rather is a learned behavior which one can benefit from.