Picture this, the sum total of your being is an empty vessel. It's a very crude empty vessel. What's it supposed to hold? Compressed light. Light, infinite light, under unimaginable pressure such that it will be contained within this now-empty vessel. The problem is this: You, the crude vessel, are riddled with imperfections. There's no way you could possibly survive the pressure of being filled. Before we can get to the purpose of the vessel, being filled, containing something, we need to perfect and complete this crude vessel.
That's this life, this world, perfecting the vessel. The world to come is what happens when the vessel is filled, or fulfilled. In our daily lives, with each mitzwah we seek out, we are hunting down those imperfections in the vessel and polishing them with the intense heat of Ahavat HaShem and Yirat Shamayim. Every now and then, the more the vessel is perfected, it is tested with the most minute amounts of light. Filled ever so slightly, so that the stresses on the vessel will reveal even more subtle imperfections. This is life, the revelations of Godliness, and the challenges of our daily toil, all to become a master craftsman, in hebrew that's an אומן, and complete the vessel. (I believe it was the Pri Ha'aretz that points out that Emunah shares the same root as Oman, a craftsman, because Emunah is something we perfect through constant effort.)
Today I came across the Noam Elimelech (Parashath Ekev) who fleshed out and sourced the idea nicely. He said that our Ahavah and Yirah coupled with our mitzwoth are what make the vessel a proper vessel. Then, just as when someone comes to you and asks you to borrow some oil or wine, they bring with them a vessel to carry the oil or wine back, in the very same way, we bring HaShem this vessel, and He fills it with His light and returns the vessel to us. This is the meaning of the verse מה ה' אלוקך שואל מעימך? - What does HaShem your lord [borrow] from you? HaShem 'borrows' the vessel from you, fills it with His light, and returns it.