Carlton McLeod explains in this video that one of the best things that you can do to make your marriage sweet is to pray and serve the Lord together. In fact, everything can and should be oriented towards God. There should be nothing more important and more fulfilling than serving the Lord together.
Colossians 3:23-24 (NKJV) - "And whatever you do, do it heartily, as to the Lord and not to men, knowing that from the Lord you will receive the reward of the inheritance; for you serve the Lord Christ."
I found that one of the most wonderful and most consistent things that you can do to cause marriage to be sweet is pray. Prayer in the household, pray together, pray with your family, and serving the Lord together really helps a lot. In other words, the household being oriented towards Christ and his work, the marriage being oriented towards Christ and his work, and even times of fun being oriented towards Christ's work, serving the Lord together as a couple, serving the Lord together as a family, creates many, many sweet moments that to me at least, I mean chocolates and flowers are great, we should do those things, but it's not nearly as life transforming as serving the Lord together and being united in a singular vision of Christ and Him crucified and communicating the gospel to the world through your marriage. And that's actually what Paul was getting at. One of the things he was getting at Ephesians chapter 5 is a married couple communicates Christ to the world, communicates the gospel to the world.
The husband taking up the picture of Christ in the in the marital narrative, and the wife taking up the picture of the church, the humble and submitted bride in the narrative. And when we are again as husband and wife looking at Jesus and talking about Jesus and walking with Jesus it communicates something to the world and communicate something to our children and those are I think the sweeter moments that some of the other moments are built upon.