Create a Forum Space.
Be open for new ideas, change. Think of modern trends, etc.
Anything to break the habits. Respond to inspiration, to new streams.
Have "Relationship Ambitions"
Material, business, travels, discoveries, projects, etc.
Maintain a dynamic individual integrity
Maintain activities where you are not together with your partner. Keep space for "external friendships"... "Time off"... Allow it to happen and go for it, even if you might miss the other person during that time.
Refreshing Life Style
Take time to be in nature. Go out. Do something physical, sports, outdoors. Eat healthy.
Give attention to your sex life.
Create Romance, Flirt, Play.
There must be a place in the relationship where you can be like kids, young teenagers. Plan a romantic holiday.
Dynamise your social life as a couple
Go beyond family and usual friends. Be an "interesting" couple, a "generous" couple.
Have a harmonious material base
Live in a place you like. Healthy finances. Harmonious work/free time balance.