Back when I was in the Christian mindset, serving the Lord had something to do submitting ourselves to the will of the Almighty God, whatever and whoever that might mean.
Life Processes, responsibilities. Throughout the course of each human's live we each have various responsibilities ("callings") that we are called to do to make life run smoother for ourselves and for others. When many people are young they don't want to be "saddled-down" with these responsibilities. Rather, they want to be free to do whatever they want.
Nowadays the phrases "Serving the Lord" has taken on a whole new more meaningful and realistic flavor, "Serving (Submitting to "the") Life's Ongoing Responsibilities of Daily living." Life is a whole lot more complicated for those who are living as adults in this culture that it was when they were children. As children everything seemed to happen almost automatically almost magically. The food was put in front you, you had a warm soft place to sleep. You had clothes to wear. You were taken wherever you needed to go.
At this point in my life I look upon the phrase "Serve the Lord" as an alegorical statement of someone being ready to step and take their place as a cog in the machinery of life. When we are young we often think that we want to be one of the big important wheels in the the machine
Submitting to, and stepping up and becoming, a cog in the great machine gives us meaning and purpose in life. We realize that we are part of something bigger than ourselves
When we serve others best is also when find our meaning and purpose in life.
And it's not just stepping up and doing one of life's responsibilities well. Rather, responsible people are juggling many many responsibilities all at the same time. There is so much to learn about each and every one.