I don't want to assume that your dwelling now isn't about bad things either. For instance, even if I'm dwelling on good things in the past, it may be because I feel like I have nothing in the present. In that case, dwelling is still about something negative, it's about how much better my past was than my present or sometimes perceived future.

Do you feel like any of this relates? If not, then I would say it's a good thing, and completely agree with jimpomer.

If it does relate, then... well I still agree with jimpomer! You can try to make the present just as enjoyable. Though sometimes that seems easier to say than do. What is it like for you?