You shouldn't go back on your word.
Mark has agreed to help George paint his house on the weekend.
Mark wants to have a fun weekend.
Mark asks other friends to join him and George for a house painting party.
Mark cancels his plans with George and goes to the shore for the weekend.
Mark is able to help George and have a good time with his friends.
Mark feels bad for bailing on George so isn't able to fully enjoy himself.