When your relationship was new, I am sure you put much time and effort into make sure you knew your loved one as well as trying to please him. That shouldn't stop once you have "harvested" a marriage relationship.
You need to continue to plant and sow seeds of love, time and commitment. Any farmer/gardener knows if you just leave a field to itself and stop working it, it will quickly be over run with weeds which will choke the life out of the fruitful plants.
Continue to work in the garden of your marriage. No marriage will ever be perfect or free from weeds or outside forces trying to get in.
2 Corinthians 9:6
But this I say, He which soweth sparingly shall reap also sparingly; and he which soweth bountifully shall reap also bountifully.