A country you can never visit

I've been thinking about the nature of regret. I think it's pretty clear that regret is most often about something that happened in the past. It could be something you did, or didn't do. It could be something someone else did or didn't do, that had an effect on you. It can be generalized or localized. But a key element of regret is its focus on the past.
Can we change the past? What effect does regret have on the past? Or, is regret really about the present, even though it seems to be focused on the past? Our feelings about the past are always happening now, after all.
We can never visit the past, not in a real sense. That is the nature of humanity. We live life in a linear fashion, ever moving forward. It is only our minds that visit the past. Our minds can do amazing things, using memory to relive, alter, glorify, condemn, excoriate, justify, exonerate...regret...
But it's all in our minds. We don't ever go back to the past in reality. What if we could? Would we be able to release regret if we could?
This weekend, I heard someone say, "The past is a country you can never visit." It was a timely reminder to bring myself to the present. Regret is a trick of the mind to try to visit the past. Staying in the present is a way of letting go of regret. It is a continual process, for some reason, because we, or at least I, tend to relive past moments.
What would it be like to never have any regrets? What would it be like to always live in the present? It's how I imagine heaven to be.....talk about a country you can never visit! :-)