Some favors come with invisible strings. You’ll only notice when they start pulling.

Help given with conditions attached rarely states them. The arrangement feels warm at the time and only becomes visible later, when something is asked for and refusing turns out not to be an option. The strings were there from the beginning, and you had no way to see them.

Notice whether a favor arrives with a mention of what was done for you, or a small note about what you might do in return. Where you can, keep the exchange even and close it out. Where you cannot, accept the help and hold the likely cost in mind.