Remember, when demons are gone the area must be filled with God’s Spirit or it will be an invitation for them to come back — more and worse than before (Matthew 12:43-45). Casting them out is one thing, keeping them out is another. Close the opening (by confession and covering with the blood of Jesus) and fill the space they occupied in your life with the Holy Spirit.
It isn’t my purpose here to go into detail about being filled with the Holy Spirit for many fine books cover that subject quite well. Suffice it to say that immediately at salvation each person receives the Holy Spirit (Ephesians 1:13; I Corinthians 12:13). He never leaves (Ephesians 4:30). Each believer has the Holy Spirit indwelling him, but not each one has the Holy Spirit “filling” (literally “controlling”) him (Ephesians 5:18). Allowing Him to fill/control us is a moment-by-moment responsibility. It means we must be 100% yielded to God in all areas of life (I Thessalonians 5:19), not allow any known sin in life (Ephesians 4:30), and to depend on Him and His strength in every area of life (Galatians 5:16). This way there will be no strongholds (openings) reestablished (II Corinthians 10:3-5).
We all are either moving ahead or moving back. We cannot be dead still at the same place. If you aren’t growing spiritually then you are fading. Continue to grow spiritually. Focus on the basics of the Christian life: prayer, Bible study, fellowship, worship, witnessing, etc. Sometimes growth comes in spurts, other times there doesn’t seem to be much outer change (it is during these times that your spiritual roots are going deeper, getting you ready for the next growth spurt). The same is true in nature, there isn’t always sustained growth, things grow in spurts.
Do NOT focus on Satan or demons, always thinking about them or fearing what they will do. Do not look for “a demon behind every bush.” They love this attention, even if it is negative. It keeps your eyes off Jesus and on them, and that’s what they want. It is important to have balance in this area of spiritual warfare. Keep it in balance. It is one of many important spiritual tools for growth. Don’t neglect the others for this one.
(If I can answer questions or offer personal counsel, or if you would like a free copy of my Spiritual Warfare Handbook, email me at Jerry@ChristianTrainingOrganization.org or download it from http://sw.christiantrainingonline.org/. My next book, Spiritual Warfare in the Bible, which is a more advanced treatment of spiritual warfare, is also available there for free.)