I find a good way to reconcile it is to not over-think, and be open to other things. I know this might not be popular with very devout Christians, but I personally have managed to reconcile Christianity with Slavic and other pagan traditions.
I believe that religion is a mystery, the Orthodox Church says the sacraments are as much. As such, if you wish, you can choose to view Slavic deities through the eye of Christianity, or Slavic heritage through that viewpoint.
I would suggest reading up on the old slavic gods and also try to research into Orthodox and Catholic saints of Slavic origin. Find ways that various religious holidays are celebrated by Slavs that varies from the rest of Christianity. That should give you some sense of how and why Slavic heritage fits into Christianity.