Marriage is like a garden.
It must continuously be nurtured and tended to.
The problem with a lot of couples is they treat marriage like buying a sofa. They shop all over town to find the "right one" and when they do they find a spot in their home and let it sit there for years.
"I'm so glad to be out of that dating scene" or "Now that I'm married I can RELAX and not have to worry about impressing anyone!"
The reality is marriage like employment is an "at will" contract. If one (stops) doing certain things the relationship is likely to be terminated.
No one is planning a divorce on their wedding day. However there is no such thing as a "cruise control" in marriage You're either "growing together" or "growing apart".
Communication is the GPS for letting you know where you're headed.
Like having a garden there is (always) something to do. (seeds to plant, fertilizer to add, watering, weeds to pull, fences to install to protect from pests.
However if it's "true love" it's not seen as "work" but rather a "labor of love". Doing whatever is necessary to maintain (something you chose to have) is being responsible. It's only hard if your (heart) isn't into it.