Tug-of-War

If you lose your balance and fall to the ground because the floor is wet, what verb describes that action?

What is the opposite of the adjective "tight" when talking about a rope or clothes?

"It is raining heavily outside, so wearing a warm waterproof coat and boots instead of high heels is very..."

"I might forget to call my mother tonight. Please..."

"The lack of sleep began to seriously ________ his concentration during exams."