Exercise your mind through meditation. It’s easier than you think:
I especially liked the comment about how it’s just a process of trying, failing, trying again (and on and on). Just like language learning, failure is part of success. The video recommends just 5 or 10 minutes a day. It’s another idea for your Summer Challenge.
BTW, the guy narrating the video is Dan Harris, a TV journalist who famously had a panic attack on live television and used that experience to do something about his self-doubt and “that voice in your head” we all have that tells us we’re not going to succeed. Here’s one video about his story.