How might one overcome the isolation caused by the passing of a best friend?

After a year and a half of varying levels of coping abilities, the renewal of social activities and contacts would probably do the most to improve inner resolve to adjust to the change. Bereavement support groups and peripheral friendships have offered some respite from the confusion, though a bigger effort to better the overall healthiness of present circumstances is clearly necessary. Changing the city of residence (to areas of either the NE States or Western Europe) for a new start—the last time I made a move like this, years ago, I met the person who became my best friend!—is currently under consideration. Thanks for the thoughtful responses.