An investment said to have an 80% chance of success sounds far more attractive than one with a 20% chance of failure. The mind can't easily recognize that they are the same.

This quote means that the mind can’t appreciate or understand that an investment that has an 80% chance of succeeding is the same as an investment with a 20% chance of failing. In other words, when considering whether to invest in something, the prospect of failure appears to be more threatening than the possibility of success, even though both have the same outcome. The 80% chance of success may seem more attractive because it appears to be less risky.