Unconditional positive regard is the most important factor in healthy personality development because it sets the tone for the child's future choices regarding his interaction style with his environment.
For example, a child who experiences a bond of love and trust with his parents despite his actions has no need to hide parts of himself of which others might disapprove; it follows that he will avoid repression and denial as default defense mechanisms.
A child experiencing conditional positive regard soon learns that he must showcase certain attributes while cloaking others, leading inevitably to an irreconcilable gap between real and ideal selves.
healthy personalitynurtured in unconditional positive regard
best defense mechs (maximize problem-solving effectiveness, minimize mental stress) + rational beliefs + fast adaptation + reaching for ideal self