The first part of the psalm stresses that no matter how hard we try, the Lord is the one who accomplishes things. I'm thinking about the plan that Naomi came up with to help Ruth get a husband and Ruth's compliance. They did work hard, but the psalm is reminding me that even with their effort, they had God to thank when things turned out so well for them.
A quibble with the connection of the story of Ruth and Naomi and this particular psalm. The psalm uses the imagery of battle to express gratitude for sons; Ruth and Naomi, not.