Possible Clues:

• Have high aspirations
• Shoot for the moon
• 'Shoot for the moon!' ... or a hint to interpreting the clues to 17-, 25-, 35- and 51-Across
• Have ambitious goals
• Be a dreamer
• Shoot for the stars
• Inspirational motto
• Have lofty goals
• “Shoot for the stars!”
• Be ambitious