Salam alaikum

I have had a terrible nightmare which scares me and makes me feel frightend and distressed.
I know that bad dreams are from shaytan to make us scared and in grief. I also knw the ahadiths of prophet Muhammad SAW to spit on the left and not tell anybody of the bad dream, for it wont harm him.
Now the problem is i mostly tell my nightmares to my mother or smone else..Im scared that i did something wrong now..Why is it so, that one shouldnt tell anyone the nightmares he had? why will it harm him otherwise? am i safe after disclosing my nightmare? im so scared as the dream was very disturbing.
Thanks Jazakum Allah khairun