I was wrestling with this question a few years ago after tangling with depression for a couple months and nearly attempting suicide. When I came out the other side, I was struck by how thin the barrier between my existing and not existing became for a while there. It occurred to me that all the pain I felt, all my suffering, wouldn't have been a blip on the universe's radar.

I realized that my individual life was very small, and that there were many others like it. I felt this sickening surge of meaninglessness. Individual glory and self-aggrandizing seemed pathetic before an overpowering wave of anonymity. What was the point of trying to achieve, why should I struggle and strive, if eventually all I am and was would be subsumed and worn away by a dull gray sea of fellow humanity?

Well, that kind of thinking would just get me back to suicide again. Eventually I decided that effort, pain and struggle was worth it if it was directed at lifting the whole rest of the sea up with me. I decided that resisting my commonality with my fellow humans was a lie, and that true meaning lay in embracing it.

To get to the point: If you want a direction to grow in, look to other people. If you want transcendency, go care for a stranger. If you want meaningful connections, then give a shit without a thought for yourself. If you want pride, or greatness, find it in well-earned gratitude. If you want to feel alive, to be daring, to not be boring, take all of the above and go do it where the need is greatest and the challenges are largest.

Pardon the dramatics, this truly is what lends meaning to my life and I'm more than a little passionate about it. If it sounds like it might fit you, then go give it a try. Not sure what kind of engineer you are, but I've heard that Engineers Without Borders does good work.