Once a door-to-door sikh fortune teller told me to pour oil on the ground every Tuesday. he said it would be lucky for me. Erm, I was jahil then and did it for about two weeks :hiding: I can't remember why I stopped but al hamdulillah I did. That was downright superstition.
But we can't put every thing down to superstition. The Prophet (pbuh) forbade Hijamah on certain days of the week. Mainly Wednesdays as that was the day Prophet Ayub was afflicted with trial.
Ibn Umar (may Allaah be pleased with him) reported that the Messenger (Sallallaahu Álayhi Wasallam) said, "Cupping (hijama) on an empty stomach* is best. It increases the intellect and improves the memory. It improves the memory of the one memorising. So whoever is going to be cupped then (let it be) on a Thursday in the name of Allaah. Keep away from being cupped on a Friday, Saturday and Sunday. Be cupped on a Monday or Tuesday. Do not be cupped on a Wednesday because it is the day that Ayoub was befallen with a trial. You will not find leprosy except (by being cupped) on Wednesday or Wednesday night." [Saheeh Sunan ibn Maajah (3488)].
On the contrary, some days are considered best for Hijamah:
Cupping (hijama) is a cure for every disease if performed in its correct time. The Messenger (Sallallaahu Álayhi Wasallam) said, "Indeed in cupping (hijama) there is a cure." [Saheeh Muslim (5706)]. The Messenger (Sallallaahu Álayhi Wasallam) said, "Whoever performs cupping (hijama) on the 17th, 19th or 21st day (of the Islamic month) then it is a cure for every disease." [Saheeh Sunan Abi Dawud (3861)].
Wa alaykum assalam.