"He is before all things,
and in Him all things hold together."
Jesus is before all things. We can interpret this as an ordinal statement - one that implies rank - or as a chronological statement and implies position in time. Either one is accurate, so I don't think its important to dig in and discover which Paul meant. (In fact, he may have meant both.) In rank, Jesus is first and foremost - the Head of the Body, as Paul writes next. In time, Jesus came before all things - before us, before the universe, and even before the angels.
In Him all things hold together. Existence is not a passive thing - things hold together on their own, until God wills otherwise. Existence is active, things hold together in Him. In Jesus. By His will.
God did not just set us here and forget about us. In Him all things hold together. Every moment of your life happens because God wants it to happen. We are here not just because God wanted us to be here, but He continues to want us to be here. Our existence - each and every one of us - is a continual, conscious action on God's behalf.
That's a comforting thought, in many ways. No matter how things look or feel in your life, at this very moment, you are here because God chooses to keep you here. He has actively decided that you should go on. In Him all things hold together.