Sweet Montague, be true. Stay but a little; I will come again. 2.2.144-145
Romeo and Juliet Capulet Castle
O blessed, blessed night! I am afeard, Being in night all this is but a dream, Too flattering sweet to be substantial. 2.2.146-148
Romeo sneak out and meets Juliet at night and they decide to get married to each other the next day
Thy purpose marriage, send me word tomorrow, By one that I'll procure to come to thee, 2.2.151-152
This scene shows how when your dreams come from your desires they can seem unbelievable when they come true. We knows this when Romeo comments "too flattering sweet to be substantial" This just further demonstrates the beauty of dreams.
This relates to the motif of dreams because it is Romeo's dream to be with Juliet. He desires it so much that when it does happen it is beyond belief.
Shakespeare demonstrates through this scene that dreams come true and when they do they bring a great sense of joy with them.