Standard nuclear physics operates with the concepts of a potential well (40–50 MeV), Fermi energy (33–38 MeV), and the Coulomb barrier (∼1 MeV for light nuclei). However, all these quantities do not explain the main thing: why does the proton-proton cycle proceed with the release of 0.42 MeV and the production of a positron with a mass of 0.511 MeV? The paper shows that the key role is played by the energy of phase resonance between nucleons — 1.42 MeV. This attractor, obtained numerically from a self-consistent model of the hydrogen atom, is the basis of all nuclear reactions involving protons and deuterium.