Sustainability depends entirely on the level of hope, faith, and belief one has in what they are striving for or engaging in.

When it comes to relationships, whether long distance or otherwise, it depends on whether each individual person's level of faith, hope, and belief resonates with the other person involved.

Some say communication and commitment are most important. I disagree... It all boils down to how much you believe in something and the level of faith/hope one has in that belief. Without hope and faith in both individuals, it's pretty much dead in the water. No communication, or the tools of technology, will bridge that gap. It will eventually cease to exist.

On the other hand, when both individuals have faith and believe without reservations that what they have is worth facing the challenges, then it most definitely can work.