Narcissism and Shakespeare

Sin of self-love possesseth all mine eye,
And all my soul, and all my every part;
And for this sin there is no remedy,
It is so grounded inward in my heart.
Sonnet 62:1-4

Perhaps we are able to glimpse a bit of irony here. Is it really a sin to love oneself? A healthy and solid narcissism must be grounded inward in the heart so as to carry out its functions properly before the tribulations of existence.
However, at the same time that that is true, one who looks at oneself too often is lost. Becoming consumed with envy and the constant need to outdo the rest.
comments, thoughts?