Since there was less pollution in the past, people usually wore white clothes for two or more days. But today we should clean white clothing after just wearing them once for the sleeves and collars get dirty. The same happens in our spiritual environment. Around twenty or thirty years ago, people could watch over their hearts though they didn't pray for days at a time. But today we should pray every day since spiritually we live in an environment of pitch darkness. If you neglect prayer and stop praying, you will be influenced by the worldly culture that is against the Word of God.