It is said that on the night of enlightenment Buddha went through 4 different realizations in each watch of night.
During the First watch - Exploration of Individual Consciousness
Rememberance of all past lives
Buddha meditated on his past lives and saw the sufferings, tensions and trauma he went through in several life times. These past lives are recorded in Jataka Tales. This lead Buddha to expand his individual identity to include past lives also. It helps to transcend series of identitites
called Jivanamala - thread of lives.