You lost today, kid. But that doesn't mean you have to like it.
This line foreshadows what Indy will do next in the film. In specific: it foreshadows Indy’s later encounter with the man in the Fedora as the two wrestle over a precious artifact - an artifact which the two desperately want.
But the line is also important in Indy’s development. It developed a dogged perseverance in Indy from a young age, which helped him tremendously throughout his career.
I'm like a bad penny, I always turn up.
This is Indy’s life motto: no matter the situation and no matter the challenges he faces, he will always show up to a situation in which he is needed. He is relentless in his dogged pursuit for what he wants or what is in the best interests of other people - particularly people who he considers to be family.
