Woke up to my kitty dying

My favorite cat died :( idk how to process this. I woke up to him trying to breath and he would stop breathing for a few seconds and then start again. Idk what happened to him. I knew he had a history of focal seizures. He had. A bad one last week . Idk how to do this. I feel like I can’t go on. I feel like I’m going to lose my mind. Like nothing feels real . I’m scared and want my cat back