There is a process of adaptation that takes place when you enter into a new way of training. The body and the mind must adapt.
Body: Muscles, tendons, ligaments, bones, and the CNS.
Mind: Your mental outlook, mental fortitude, comfort under heavy load/high volume and comfort with increased intensity.
Based on my on personal experience and the observed experience of my athletes, the process generally does not happen within six months - in fact it usually takes a minimum of one year...