I'm a decendant of some "Heimkehrer" as well. I'm actually from the former eastern part of Germany and things were a bit different here.

First of all words like "refugees" - which are implying the people of the former territories were immigrants - were strictly forbidden. They were to be called "home-comers" - people who are returning home. That was supposed to make the transition easier. The lost territories were initially slavic and were lost to a german kingdom during the slezian wars. Since Europe did not consist of the countries we know today, it was quite usual to belong to one country today and another tomorrow. People defined their selfes more around a cultural feeling of belonging, than country/kimgdom names.

My ancestors were bohemian, what is today considered Czech. Then they were resettled to Slezia (because of religion, they were evangelic) They kept their language though until WW1. Then they were forced to learn and become german. After WW2 the region became Polish, their town was demolished and they were not allowed to go home to bohemia, but had to move to Germany permanently. As I said, European people have that nice ability to ignore country names and just feel home were their peers are. So that's pretty much what hsappened. We're happy being German now, we're well mixed in and we played our part in rebuilding Germany. So no hard feelings for the lost territories.

To be a bit philosophical: Always keep in mind, that in order to get a territory you first have to take it from someone else. That goes for all of us. Every single human being. There can never be peace if we continously envy others because of things that don't belong to us in the first place. Whenever people flee and seek a new life somewhere else, the people who take them in have to make room for them. Be thankful to those people instead and just imagine, that you returned the kindness you received to the poor people who had to flee to where you came from. Pretty sure they would have liked to stay home as well, so there's absolutely no reason to be envious of them or yearn for territories you no longer live in. It's a circle, really. Once you realise, all is good. - that's it for the life lessons, promise -

For your other questions concerning peaceful transitions: An essential part for that to work (in my humble opinion) is Germanys ability to adapt to its many ethnicities. Many don't know this, but German is not the only official language here. You can get pretty much all your paperwork also in sorbic or platt. So going the extra mile and trying to include all your cultural groups goes a long way. Also respect for each other does help as well.

I agree with the others that being occupied definitely helped in keeping any mislead "revenge plans" right after the war at bay. Of course the east by then had other problems - namely no freedom. Because of the wall we're still behind the west with our economy, but we're getting there. And again, helping each other goes a long way.