An update to this for those of you so inclined.
Stand tall and strong, feel yourself at the centre of your own reality, with infinite potential and infinite power - this this does not come naturally, act the part as though playing, let go of all inhibitory thoughts based on everyday reason, and recite:
"I am the One who accepts no masters
I Am.
In the name of the Most High, I command you to depart."
This may work better for those for whom “most high” (alone) raises any lingering emotional resonances of religions.
Inverted pentagrams traced in the air are also successful in removing some of the energies you may find.
On the above theme of sealing things in metal, keeping doors closed (without becoming OCD about it) is also an ancient family superstition handed down to me, you’ll see it referenced in the idea a closet door left slightly open is a bad thing in various fictional portrayals as well.
I’ve spoken about the use of stairwells and doorways as liminal spaces a few years ago on here.