I've always believed that you best serve others when you are in good form yourself. You can't pour water from an empty bucket, and you aren't as able to be helpful to others if you are struggling yourself. So I've always promoted taking care of yourself as important when taking care of others. But maybe my view has been too shallow. It still pushes the idea that "you" are separate from "others."
In Bringing Home the Dharma, Jack Kornfield notes that we are all interconnected in the world and there is no "us" and "them." Now I've heard this before, of course, and understood intellectually that we can't see others as different from ourselves. But he takes it a step further and asserts that since we are others (oneness), when we care for ourselves we are taking care of others. In other words, if we are truly part of the world, when we care for the world we are caring for ourselves, and when we care for ourselves we are caring for the world. We are not separate from the world we want to help. If we feel compassion toward all sentient beings, that entails---obligates---having compassion for ourselves. It isn't a matter of selfishness or self-sacrifice. It's all part of the same thing. We don't feel guilt for tending to our own needs, because it's inherent in tending to the world's needs. If we still see ourselves as separate from other people, then it does risk becoming self-serving. But if we approach it from a stance of loving-kindness toward all beings, it changes the very nature of it.
Which puts a deeper twist on the scripture "Love thy neighbor as thyself." Not "Love him as much as you love yourself." But "Love him because he is yourself. And you are him." The "as" takes on a different meaning.