According to Joseph Butler's Fifteen Sermons preached at the Rolls Chapel, there is a specific text within that refers to "Altruism and Self-Love" (1726) Joseph Butler defines self-love as
the effort to control and manage passions so that the individual can live happily -- in virtue rather than in vice
Therefore, to Joseph Butler self-love is a positive thing because it invites humans to seek for their own happiness. When you deny yourself that self-love you repress a number of healthy processes and hence you become disturbed. Self-love entails a higher search for self realization by accepting ourselves and understanding exactly what is that will help us live our lives in complete peace of mind. This is happiness. In Butler's words,
...from what appears, there is no Ground to assert that those Principles in the Nature of Man... are more generally or in a greater Degree violated, than those, which most directly lead us to promote our own private Good and Happiness.
Self-love is, then, an extension of benevolence and is by default completely compatible with it. This is because, to Butler, the nature of all human beings is essentially "good". In Butler's words, benevolence entails the way in which the individual wants to interact with the immediate society. Since benevolence is at the core of our personalities, and self-love is a manifestation of benevolence, then
"a person who is benevolent will help others to live happily. Whether... arising from self-love or...from benevolence, virtuous actions are natural behavior".
Once we love ourselves enough to find our own happiness, we feel a natural need to want happiness for others and help them find it. It is no different than those whose basic needs are satiated; the more psychologically healthier you become, the more empowered you feel to help others get there too.