To answer your question, the enemy's negative energies are immediately perceptible, precisely because they are characterized by a great deal of anguish.
Most of the time, it's just psychic manipulation, which is even worse than a hypothetical touch, because if you have a rather weak mind, it's not difficult to fall into the enemy's trap. My advice is to purify and protect yourself at all times.
Make sure that the enemy cannot find any weak points to bother you.
Despite this, I can already tell you that the last point is not something that happens immediately; it takes a long time to achieve complete purification. Never underestimate it.