I've been really struck today by three words in Psalm 2:11.
rejoice with trembling
The context is how we are to respond to God's enthronement of Jesus as King, ruler and judge. We should rejoice in him - actively expressing joy, overflowing and delighted in him, but we should do so with trembling - not of the uncontrollable shaking type but out of fear. God is not tame. He is all-powerful and very very scary so we should tremble before him. But because we take refuge in him (v12), his awesome and scary power is a cause for great rejoicing.
A difficult balance, but an important one.