One thing I realized more and more as I got older is that no one really cares about anyone else. If you want to be friends with someone, or be a part of someone's life (and vice versa), you have to impose yourself on them. For example, if you want to play tennis with someone, keep bothering them about it. If you want to play video games with someone, keep bothering them about it. Sometimes it feels difficult or socially awkward but if you keep doing it, it gets better.