Get them to play with a much aggressive double partner or a much better player. That would break their mind and heart and humiliate them. Take every chance you get to add insult to injury 'Hiya Bob, Mike said you lost 2-11. You'll get there. It's just 2023. The next Olympics isn't until 2028, you've got time'
or "I know a coach in <California> who can work wonders with you. Why don't you fly out there, practice with him, stay a month and come back?"