A variant of "don't bite the
hand that feeds you", 'Don't shit in your own backyard' means don't trash a good
thing, take advantage of or ruin a close relationship. If you have a positive situation or loving or giving person in your life, you should be careful to protect it/them. When you
abuse the situation, person or relationship and deliberately commit an act that you know is potentially harmful or injurious to the situation or person that is good to you, you
run the risk of ruining it. Any act that you know would
hurt the one with whom you are affiliated and potentially ruin the relationship forever if they found out. The hospitable one (the house with the
yard or security) is fouled or injured by your actions (shit upon) which ultimately poisons the soil (the growth medium, sustaining qualities that nurture). Conscious or willful sabotage through
selfish actions that generally involves planning and premeditation but can be impulsive. An ultimate act of betrayal through a degree of separation that taints or destroys a perfectly good
thing or relationship for no good reason.
Examples of "don't shit in your own backyard" would include pursuing/sleeping with your best friend'
s or bosses' spouse or significant other; pursuing/sleeping with a mentor's friend; pursuing/sleeping with a friend's close friend that you're interested in; using a person to get close to another; stealing your parent's/friend's car; ditching a loving parent for another
adult; keeping secrets you know would further
hurt the injured
party; wiping the house you're staying at clean; stealing from a friend or relative.