It is narrated from Hazrat Abu Bakrah (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: None of you should say, "I stood (in prayer) for the entire Ramadan," (because there is no way to avoid heedlessness or sleep; it is possible that on some day he may have slept through it).
Hadith Referenceمسند احمد / أول مسند البصريين / 20489
Hadith Gradingحکم دارالسلام:إسناده ضعيف، الحسن البصري مدلس، وقد عنعن