strength comes from trust
This is a story from when I was teaching qigong in the countryside in Hebei Province in 1994. Generally when teaching qigong, the students invite you to eat your meals with their family. One morning, on the way to a student's family, a student suddenly called out to me. Her niece was giving birth at home with only a midwife but she was not managing to push the baby out. I had no experience in this matter but I knew the woman trusted me. So I said to her that she could do this herself; she should send qi to her niece while thinking that her hand was mine. She at once returned to her niece, sent qi and on the third try the baby was born.
Teacher Pang said "xin li", meaning xin de li liang", that power comes from your full belief.