There is no diety except Allah, I seek Your forgiveness,
I beg Thee of Jannat-ul-Firdous and I seek protection in Thee
from the fire of Jahannam

We have been commanded to do four things excessively in the month of Ramadaan, two of which is for the pleasure of Allah Ta'ala and two things are such that we cannot do without. The two things that are done for the pleasure of Allah Ta'ala is excessive recitation of the Kalimah Tayyiba and Istighfaar. The two things which one cannot do without is to beg of Jannat and seek protection from the fire of Jahannam. The above Dua comprises of all these four things thus we should recite it as often as possible.