In other words, doing good for the world gives not only Clark's differences, his powers, meaning, but it gives his whole existence meaning. Speaking to Jor-El, as Jonathan predicted, only clarified the specific dreams and goals his biological parents had, but from an early age Clark was taught, as many Christians and likely people of other faiths are also taught, that whatever god they pray to created them with a purpose. Clark begins to want to seek his purpose as a teenager: "I'm tired of safe. I just want to do something useful with my life."
I highly recommend reading Mark Waid's essay
"The Real Truth about Superman: And the Rest of Us Too" because it aligns almost perfectly with what I and the films have expressed about Superman's motivations. Here's an example. After years of loving and working on the character, Waid writes that "the one question I could not answer [was] why does [Superman] do what he does?" The essay follows several of his trains of thought, but he ultimately concludes "When [Superman] lives as who he really is, in full authenticity to his nature and gifts, and then brings his distinctive strengths into the service of others, he takes his rightful place in the larger community, in which he now genuinely belongs and can feel fulfilled. [...] In helping others, Superman helps himself. In helping himself, he helps others." He adds, "Kal-El knows instinctively that it is only when he puts his gifts to use that he truly feels alive and engaged."