Please provide sources around the idea of "enduring" pain. Zen, and Buddhism in general, focuses a lot around compassion. People can encounter quite a bit of p

Please provide sources around the idea of "enduring" pain. Zen, and Buddhism in general, focuses a lot around compassion. People can encounter quite a bit of pain from sitting but the advice is to relax and "let go" of the suffering as much as possible rather than "soldier on".