When you have a bad suspicion about a Muslim in your heart, you should increase your consideration toward him and make dua for him. This way you will infuriate Satan and will be able to drive him away. Because of this, Satan will be reluctant to put evil thoughts into your heart, afraid that you would increase your consideration towards your brother and will make dua for him again.
Al-GhazaliNeglect not your time, nor use it haphazardly; on the contrary you should bring yourself to account. Structure your litanies and other practices during each day and night. This is how to bring about the spiritual blessing (baraka) in each period. If each of your breaths is a priceless jewel, Be not like the deceived fools who are joyous because each day their wealth increases while their life grows ever shorter.
Al-Ghazali