You have no reason to be sorry, other than for the loss of Boots. We cannot control these things, timing isn't always on our side. I know Boots knew your love for him. He is waiting for you, patiently, on the other side. He will let you know when you meet up again, his eternal gratitude for letting him go.

RIP, Baby Boots. Meowmie is in such pain right now. Send her a message that you are free of it now, playing happily, like a young kitten, with all of our pets that have gone on before.