I've always thought that questions that put "life" and "meaning" into the same breath deserve the old Zen response, "mu". The question should just be unasked, because it's nonsensical. Meaning implies communication. If my life is treated as a "communication", then it's a very bad one, because there will be practically no consensus on what it is trying to say beyond, "Yup, I was here, just like you." When you ask the meaning of a sentence, you don't say, "Yes, that's what the sentence says, but WHY is it THERE and WHY did it SAY THAT?"
Now if you want to talk PURPOSE, that's a more meaningful discussion, but still a bit nonsensical. The purpose of my life? THE purpose? I can have only one? All the time? I can't have different purposes at different times of my life, or times of the day, or even multiple conflicting purposes at the same time? And ultimately, doesn't it all come down to the same thing, whether or not you believe in an afterlife? Just to...go on? (and on, and on, and on)
Service to Jesus, whatever that means for the person claiming it, is but one purpose. If you don't believe in Jesus, okay, so you have one less purpose than I do, just as you believe in one less god than I do. Or maybe you're just less ambitious as far as going on and on and on, with no belief in the afterlife and all.