God tells us it is good for us to wait for him.
The LORD is good to those who wait for him, to the soul who seeks him.
It is good that one should wait quietly for the salvation of the LORD.
(Lamentations 3:25-26)
Here are a few things God does for us when we wait for him:

He humbles us:
Waiting helps us realize that we are dependent creatures. We’re not the captain of our souls or in charge of our own destiny. We’re not self-sufficient, but we live by every mercy dispensed from God’s hand.

He teaches us to seek him:
Waiting on God is not passive. As we wait, we seek. We pray, we beseech God. We cry out “How long, O Lord?” We ask, and knock and submit our requests to God. If we got what we wanted right away, we wouldn’t draw near to God and we’d miss out on the joy of his presence.

He teaches us to trust him:
While we’re waiting for God to save our child or meet our needs we stretch our faith to the limit. We trust, though all our circumstances tell us to despair. As we wait, our trust grows.

He builds patience and perseverance into us:
The only way to get patience is to have to wait for something. Perseverance only comes through enduring trials, failures and persecution.

He reveals what is in our hearts:
What comes out of your heart when you don’t get what you want? Grumbling? Hard thoughts of God? Or praise and trust? When you can wait with a quiet heart, you know God has done a work in you.

He helps us to treasure him above the things we are waiting for
He teaches us to find our contentment in him. He is our portion, not anything in this world. Only Jesus can truly satisfy us. No person or thing that we wait for can satisfy us like Christ.

He makes mercy sweeter when it finally arrives:
We appreciate blessings more when we’ve prayed and trusted and waited for them. We appreciate health more after sickness. And how much more will we enjoy our eternal weight of glory after our temporary, light afflictions.