In any level of the game, enter this timed sequence to have the biggest life bar available and refill it. You may need some practice to do it since it's timed: listen to the thematic music of the game, which does something like "tam, tatam, tatatatam" and reproduce the timing using the right (or is it left? sorry it was a looonnng time ago) trigger. When you read the sequence, 'R' is "hold right trigger", 'r' is "release right trigger" and '...' indicates a small duration. It's really easy to do once you got it: all in all, you're just going to press the R button four times.
|R ... r R ... r R r R||maximum & full life bar|