Would you have sympathized with Jack's feelings towards his wedding?

I've seen this film two times in a short amount of time, I really enjoy it. But there is one scene that just gets me. Perhaps it was better covered in the novel, and that's Jack's confession to Miles about his feelings towards Stephanie and his wedding. There are a couple things that I can take away from it.

1. Miles and Jack have known each other for quite some time, therefore Miles knows Jack is implosive and his interest in owning a vineyard and living with Stephanie will dwindle quick.

2. Miles is so miserable he truly doesn't want anyone around him to be happy.

But in some way this doesn't make sense because Miles doesn't like his job, he loves wine and it's culture. Moving out with a close friend to wine country to start a business, maybe even with the girls. Maya is even getting her masters in horticulture and is unsure what she is going to do. It seems like the perfect storm. No?