In my 5 years of gardening, I have dealt with many clients. But I have to say, the majority of the difficult clients tend to be the average people. They want absolute perfection and for the very minimum price you can give them. They will argue over every last penny to make sure they are getting the utmost effort for their money. There are also some requests that surprises me while working,  a client would looked at me in the eye and tell me "Mr Gardener make sure all the leaves in the gutter is packed",  "can you please clear all the weeds at the backyard".
I always tell them that my job is a landscape gardener and not a casual labourer, sometimes I do the clients request. After working with my tools, I packed them take a rest and go home. On reaching home,  I have cool shower, eat and relax well. In some cases I do have back ache which makes me take painkillers. I love the work, because I derive joy in making gardens look attractive and beautiful.