Hazrat Shaikh Moulana Muhammad Zakariyya (rahmatullahi ‘alaih) once mentioned the following:
Reciting one’s dhor of the Quraan Majeed in one’s nafl salaah can greatly help one to remember the Quraan. I have experienced this personally and many of my friends have also witnessed this.
From the number of paras which one has memorized, one should take a minimum of half a para daily and recite it once or twice while looking into the Quraan Majeed. Thereafter, one should try to recite the same portion throughout the day and night in one’s nafl salaah such as awwaabeen, tahajjud, etc. One should at least recite the portion once or twice. This practice is proven to be extremely effective in remembering and preserving the Quraan Majeed. (Qutbul Aqtaab Hazrat Shaikhul Hadith Moulana Muhammad Zakariyya (rahmatullahi ‘alaih) pg. 459)
Source: Ihyaauddeen.co.za