Answer:
Vincent is likely referring to Erikson's psychological stage 5, which is called "Identity vs Confusion".
Step-by-step explanation:
Erik Erikson as a psychologist who specialized in the ego. He created one of the most popular theories on psychological development. There are 8 stages that conform the whole theory.
The way Vincent feels is referring to the stage 5, which happens during adolescense. The stage is called "identity vs confusion" because it is the moment in which the individual start to explore their independence and develops a sense of self. The fact that Vincenyt, although an adult, still feels like he has no personal identity speaks about him not being able of building up confidence in himself and his persona during his teenage years.