Think of this example: A driver may know that to maintain his car and keep the engine in running order, he must regularly change the oil.
فَيَقُولُ فِي نَفْسِهِ :‏ ‹ إِذَا لَمْ يَكُنْ لَدَيَّ وَقْتٌ لِتَغْيِيرِ ٱلزَّيْتِ ،‏ فَسَيَبْقَى ٱلْمُحَرِّكُ شَغَّالًا فِي ٱلْوَقْتِ ٱلْحَاضِرِ عَلَى ٱلْأَقَلِّ › .‏