The correct answer is optimal.
Positive psychology could be defined as the scientific study of what makes our life worthwhile, but without forgetting our personal problems.
Positive psychology promotes a balanced anhancement of our strengths, of giving us more objective view of ourselves. This is necessary because some strenghts are not good either by excess or by default, such as positivity. Being too positive can make us believe that we are invulnerable. It can make us believe that we are going to achieve, and lead us to assumen too many risks, get involved in too many projects at the same time , more than we can carry out. If we are negative, on the contrary, we can not enjoy what good life has.