If its just the gig in the park you wished you could have done, then you'll get over it, it's just a one off, gone when it's gone. But if you are feeling you'll miss the next steps the band may take due to that gig and direction then you may need to reconsider the decision, and if that's not possible, then make some serious efforts to become happy with it. I've met a fair few people who have a what if story and they haven't moved on in years.
Re, depping, if that's your binding rule then fair enough, don't think it disrespects anyone else, I dep for a few bands who wish to keep their covers/functions things going when a member can't make it, works for me, I'm not offended if anyone sees that as lesser?