The part of you that can carry a lot on your back. Do people often expect you to carry the heaviest workload because you are the one they can rely on? Do some take advantage of you for your abilities? Are you being stubborn by times? Do you sometimes get frustrated with trying to be the good one and just wish you could let go and roll around in the dirt?
See Donkey, Animal, Power Animals, Farm, Job, Heavy, Baggage.