While it is good to clear out your environmental space, or exorcise the building with any of innumerable methods, or apply feng shui principles, the real target is your energy body and that is what you have to work on. It doesn't matter what times you practice. In the interim, you should always invoke your masters' energy for protection. But this is a 7/24 effort and it may require the help of experienced professionals as listed above.
Once you are clear, then you have to stay clear. Good luck! (In a matter of speaking 
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