When someone leaves, when someone does us wrong, we automatically blame it on ourselves, the "why am i not good enough?" "What have i done that drew them away?". And we shouldn't. Some people choose to start away a chapter with different characters not because we're out of plots or because ours wasn't adequate enough to satisfy their story but because they're looking for a different series of events which requires characters with different qualifications, and just 'cause it's different doesn't mean ours is any less or any better even.
Let them be. Remember the series of events you went through your whole life and how the characters kept changing, how some had the main role at a time and now they have none. It's not a fight or a certain event it's just how life flows around my dear.
But you know something.. what hit us is not the fact that we're out of the story but the way we're pushed away, the way they yelled FIRED. It lingers to our memory and take more space than we're willing to give. You keep rewinding it unconsciously. You forget all that logic of "it's just because they chose a different path" and focus on the "they pushed me away" fact. It's really not something they intended to make you feel, something they never thought of at all maybe, they just went with the flow and left you walking in the circles of self doubt. It might be the new WhatsApp group you're not a member in, or the text saying "my airplane's tomorrow at 7", or how they just switched classes to be with someone else, the parties and outings they forgot to invite you to, the birthday they forgot to wish you, the broken calls to check on you. It's the way they choose to slip you away is what stings.
And if you're convinced you've done no one wrong then, let them be.