Do not give the devil a foothole. Rebuke him!

  You've got to understand, once you give the devil a foothole through your thoughts, actions, or even idleness, he's going to come in, by your invitation. Then, if you don't cast him out, rebuke him, telling him to flee from you, he will stay.
And God says you can't serve two masters. Either you're going to have actions & thoughts of God, or you're going to have actions & thoughts of the devil, not both at the same time: you're serving one or the other.
  Now, your actions are produced by your Spirit, and you should have the fruits of the Spirit as listed in Galations. Outburst of anger, jelousy, fornication, greed, etc., all of these are fruits of the devil and those with his spirit.
  So, you must not do these things! They will testify against you, in this life, and come judgement day.