Love without effort is meaningless. Love is only a feeling but the actions are the ones who dictate ones happiness. The word "effort" covers everything.
Effort is all about the actions to show how much you love a person. Giving gifts, greeting her everyday, fetching her from work, or even cooking breakfast for her are typical examples of efforts. Even being patient is part of luxurious actions in love.
Love + Effort is a perfect combination to maintain a healthy relationship. I do believe sometimes in love the spark will no longer exist, but with effort to maintain it.