Revelation 4:11
You are worthy, our Lord and God, to receive glory and honor and power, for you created all things, and by your will they were created and exist.

By God's will we were created and exist. To look at it from the flip-side perspective, our purpose is to fulfill His will. Meaning that we are here to do the things that are according to His will. Worship, obey, praise, love, and the list goes on. There's also a list of things not to do, things we call sin, but that can also be called "things not of His will". It puts a different perspective on things when we don't just call it sin anymore, but rather think of it as "doing something that is opposing God's will". It (sin) takes on a bit more gravity when you think of it that way. It's no longer just doing something bad, but it is in direct opposition to the will of our creator, and it (sin) is in direct opposition to the very reason we were created and exist.