How do the fitness principles of overload, progression, and specificity apply to flexibility? (not a multiple choice, short response)

The principles of fitness help a person to improve in a specific exercise to reach the desired flexibility. If a person wants to develop strength, the individual should focus on the principle of overload, with a greater workload than usual. This should be regularly maintained as per the principle therefore leading from overload fitness.

The principle of progression means that an individual must gradually increase the workload for improvement to continue which is also easier and adjustable. The flexibility gets improved by gradually increasing the amount of time and the number of repetitions to a point when you start feeling a change. As a result this will help in progression of the individual according to the his/her body.  

The principle of specificity applies when you focus on the muscles at specific joints that you stretch. This must be habitual by the individual by the means of targeted area of the individual's body. You must work on all specified muscles that need stretching to improve overall flexibility. In spite of this, the individual also needs to sustain the food in take habits .