Stress
The stress involved with landscape design isn't like that of other horticultural careers. Most of the work is done within a nice, comfortable studio with regular working hours, so there's no undue stress about dangerous working environments, weather, working weird hours, or serpents that tempt with forbidden fruit.
The stress is mostly from rushing to meet deadlines. Landscapes need to be ready to outfit new buildings as the buildings are completed. Delays with getting landscapes approved by town councils or home owner associations are also no fun. After landscapes are installed according to specifications, there's always a possibility (or even likelihood) that the inept gardeners who eventually ruin it will want to blame the designer for faulty design.