What does it take to keep a relationship healthy and happy? It does not matter if you are married or dating, the outcome of the relationship will unfold according to how you treat your relationship. The responsibility falls on both parties to make it or break it and it should not be the responsibility of only one person.
The longer you are together the more relaxed you become around each other. As time goes by you start to become complacent towards your partner, you may take for granted the things they do and no longer show thanks like you used to.
Both of you work and are too busy with that and raising the kids, you start to fall further behind in your relationship until you are each doing your own thing, not spending that much time together. If you do not want to reach this point in your relationship, start early in doing preventive measures.
Do not forget to appreciate each other for what you do. Even the little things you do for your partner will be appreciated, like a small gift or a surprise of some kind. Doing chores around the house together can help keep you close, or do a chore for your partner that they normally do to give them a break.
As the relationship grows and moves along do not forget the small stuff that you know your partner likes. If your girlfriend or wife wants to go to the movies to see a love story which you do not care about, go with her and watch it. She will really appreciate the gesture and you have done something special for her.