We call this “having good spiritual hygiene”. In a nutshell, a combination of having up wards, knowing how to banish unwanted intruders, and raising your vibration (feel happy things more than low things) keeps nasties away and attracts helping entities.
We have a lot of topics on this forum about it as unwanted interference is a common problem, and we collected some fave tutorials and such here: 
Also, insist that you’re not weak, and not open to be walked over, you can speak softly and carry a big stick, look nice and soft but have a steel core that shows when needed. Being tough doesn’t have to compromise how you want to feel about yourself.