For any relationship to prolong the must trust each other same is the case for a romantic relationship.
While building a relationship it is always asked that both the partners should be true to each other and this can only bring trust in their lives. A little lie may lead to a heap of lies further breaking the relation. For a heart broken person its very difficult to overcome their lovelorn lives and trust someone else.
For them it is advised every person is not same, your new partner may not have the same likes and dislike as the older, there may be difference in their character so just try to keep an open mind for them. The ones who choose to be their partners should be prepared for every ball they throw in your because if you truly love them you’ll want to be with them forever. Your partner may turn hysterical at times or be suspicious in your conduct with your friends of opposite sex. Just make them understand that it is them who you love not your friend.
Love them a lot, never let them feel lonely. Best of luck.