It is obligatory to be wary of negligence and laziness (especially in Ramadhan). Take your portion of rest by way of sleep, there is no problem with that, as long as that does not cause you to be remiss with the (obligatory) prayers.
Do not allow your sleep to dominate your valuable time – the noble time of Ramadhan (due to the many blessings within it). Because it is possible that you will not reach Ramadhan again in other than this year (due to death) and thus you will be deprived of blessings and goodness (if you do not take advantage of your time now).
Shaykh Fawzan (hafidahullah) Al-Kalimaat Ar-Ramadhaaniyah – 1439