Witchipedia

Many believe that we are picking up various energies and even entities all the time as we go about our day and interact with different people and different environments. Usually, they are harmless and our energetic field normalizes through basic, everyday self-care practices of bathing, eating a good diet, getting enough rest and doing things we enjoy. Sometimes this isn't enough and you may need to do some sort of ritual cleansing, like taking a ritual bath, smoke cleansing or various other methods found in specific traditions. Many engage in these regularly as part of their self care in order to maintain aural hygiene. If these methods are not enough, you may need to consult your clergy or spiritual practitioner for more intensive methods.

Some signs that may indicate a problem include a general sense that things are off, feeling like you're not yourself, thoughts and urges that are outside your normal character, obsessing over a person, place or object, feeling like you're being watched, catching a glimpse out of the corner of your eye, and nightmares. These signs will occur a lot if there's a problem, not just once in a while. Everyone experiences these sometimes and it doesn't necessarily mean it's a problem.

You should also note that these can also be signs of mental illness and I highly encourage anyone seeking spiritual treatment to also seek psychological treatment because even if your problem is spiritual in nature and not psychological, people experiencing any sort of chronic symptoms whether they be physical or spiritual, are at very high risk for developing psychological issues too.