Loving oneself is merely the combination of understanding and accepting oneself. It's more of a skill than it is a natural thing. The way we feel about ourselves is in the natural sense is more a less a complex mishmash of how we perceive ourselves and how we perceive what others feel about us. For example, if an individual has a low self esteem, it's highly likely that that individual in some capacity is comparing his or herself to some standard. This standard, however, is predicated on what that individual believes is the status quo, or what that individual believes others view as the status quo. But this comparison in itself is unjust because it lacks to compensate for the individual qualities, behaviors and actions that make up that standard, it is merely the overall standard.
In other words, say someone is down because they don't feel smart. Perhaps they've received low grades, were criticized by their peers, or maybe they were informed that some of their family members have learning disabilities. The comparing begins: I'm not smart because I get poor grades, people who get poor grades are not smart, therefore because I get poor grades I'm, in fact, not smart. This comparison, however, is flawed. "Why" is a huge factor. Why did you get the poor grade? Maybe you didn't study, maybe you are having a hard time understanding the concepts behind the material, perhaps you are an anxious test taker. There are many things that could make up a poor grade outside of being dumb or "not smart". But this only comes at the expense of learning and trying to understand oneself. Through that process you can identify strengths and weaknesses and begin to work on those. And usually by doing so, one finds love for themself through learning who they actually are and not who they "thought" they were.