Every ending marks a new beginning. When a door closes, another one opens up. With that in mind, it should not be fearsome to put an end to one chapter; instead, we must be filled with unquenchable excitement as a new chapter unfolds. Whatever is left behind is finished, and has done its part by strengthening our hearts in preparation for a much more challenging future.
Letting go when one has quite attached oneself on a deep level to something which has to be left behind is reasonably difficult. While it may be true that there are a few rare gems which stay with us until the end of time, most of which and whom we encounter are just passers by. They stay for a while for good or bad reasons-but in any case for us to learn something from them-and then they leave. Some paths are meant to only cross, and not to combine.
Having mentioned all of that, it is safer to take life as simple as it should be taken. Allow things to flow the way they should. Without much struggle and effort, it is easier to find happiness.