Islam generally teaches that something small done consistently is better than doing too much and then stopping. Body and soul are not actually totally separate. They are integrated. Keeping healthy and physically fit is vital for the well being of the soul. Nowadays many doctors are saying that some forms of depression can be caused by an unhealthy gut; conversely emotional stress can affect digestion and therefore overall body health. Try to establish a pattern, or a good habit, when you do dhikr or other matters directly related to the soul - a time of day where you are least likely to be disturbed, or tired, or your mind overloaded. Even just contemplating the creation when you are out walking in the road can nurture the soul.