Dotsie - I think you're on the right track -- except try leaving the headphones home too. You will be amazed at the sounds of nature -- if you concentrate on them instead of talking with a friend or listening to music. You may be surprised how many different birds you have in your neighborhood -- and the different songs they sing -- maybe you'll discover a nest with new baby birds (I know -- in the summer not now )
Pretty soon - as the seasons change - you'll be able to see all the different flowers in peoples yards blooming -- see how many different bushes they may have planted. Bees and butterflies -- all natures children will start "multiplying" around you if you are focusing on that instead of socializing. So don't think of your friend's moving away as an end to your walks -- but the beginning of warming your spirit on a daily basis.
And maybe one of these days -- a neighbor you haven't met yet will pop up and ask to join you