There is a misunderstanding here. We've come to speak of people with narcissistic personality disorder, for short, as "narcissists".
But narcissism is a tendency present in every human person, and useful (for self preservation purposes, healthy competition...)
The problem is when that narcissistic tendency becomes hypertrophied and appears AT THE EXPENSE of others (you feel so good about yourself that others are just your stepping stone, you don't care about their needs, etc).
Loving oneself, and taking good care of oneself, doesn't have to incompatible with loving others, admiring their successes, helping them, sacrificing your comfort in favor of someone else on occasions... These things a "narcissist" (a person with narcissistic personality disorder) cannot do.