Invest in some chunks of Black Tourmaline. Find out how to arrange these in your room for 'protection' ... (would come under psychic-attack but ~not exactly). Seal your room energetically. Smudge.Have some tourmaline with yourself close to your body to sleep with.
Pray cleansing prayers for your aura.
Set angels around to guard.
Close guard and protect energy portals.
Maybe others here will have more suggestions on protecting self.
Ground. The Black Tourmaline will help protect from negative energies AND Ground you.
Do not entertain this 'in your mind'... as it feeds that energy. When you find it happening, with your voice say outloud STOP. LEAVE NOW. If you are a person of Faith, add the name of Jesus Christ, then let the Guardian Angels take over.... This is happening on an 'etheric' level. You can entreat Divine Protection IN that realm to help you.
If you are super into Faith (Christian), plead the Blood of Jesus. Compel the "elemental-thoughtform" to dissipate.
Remember, what you feed grows. A bird can land in your tree (mind, imaginations) and you can keep it from 'building a nest' and being cozy! LOL.
Detach from giving it any more energy.
Do the protective things I've mentioned... especially even one piece of tourmaline with you in bed for a while.
You might also take a chunk of Rose Quartz... stone of Love, to Balance the lower for the Higher Vibration.
Wishing you Great Success, and Higher Love!