Instilling confidence

I got frustrated with one of my kids tonight. I guess I was frustrated because he gave up on something outright...cried before he even tried. And it frustrated me. Let's start from the beginning:
A couple of months ago I put my son in swimming lessons. They ended up being too hard for him (even though his previous instructor said he'd be ready for the next level and had been to lessons for about two years). All of the kids were a good three to four years older than him and better swimmers. He did amazing that night in lessons, but struggled enough that we decided to drop him down a level. We wanted him to be challenged and yet succeed and feel good about himself, not struggle so much that he's scared and that the instructor has to spend a lot of time helping him, ignoring the other kids. Anyway, tonight was his first lesson in the new group. We showed up, and he got in the water. He looked, and saw that it was the "hard" instructor from before. He met some of the kids...only one was his age. The rest, oh, a good two years older. Ugh! Not sure why the lessons are for an age range of five years...anyway, he started crying and got out of the water before the lessons even started. We talked, and he was simply freaked out. Freaked out because of that "hard" instructor, freaked out about the older kids. He was so scared that it would be like last time, that the older kids would be better swimmers, so he didn't even try. Didn't even try. The tough part for me is that in watching this class I know that ALL the kids are at his level of swimming...he would have kept up with them fine! He would even have been better than two of the kids (not that I'm bias or anything!).
Giving up is a tough issue. We want our kids to TRY and to try hard. Because its good for them and their character, because its good in life to try things, even if we fail or look foolish. And because it will be the best example for Dillon. Dillon will have a harder time in certain things. When you don't have legs or an arm, I can imagine that swim lessons will be tough. And I know there will be times when Dillon will want to give up. I pray for his older siblings, that they will encourage him, that they will challenge him, that they will love on him so much that he'll be excited to try anything!
So I'm trying to motivate my older kids to try everything. To be that good example for their little brother that will have a more challenging time. And it frustrated me when my boy gave up on swim lessons before trying. We had a talk, a good long talk about being strong, about trying, even if we are scared and may fail, and about being an example to those that may struggle more than us. I tried to instill confidence, and not be frustrated. He's willing to try again next week with this class. He said he'll try his hardest. I'm praying for that.
February 14th's devotion in Jesus Calling begins with this paragraph, and I'm praying this for all four of our children. "Give yourself fully to the adventure of today. Walk boldly along the path of life, relying on your ever present Companion. You have every reason to be confident, because My presence accompanies you all the days of your life - and onward into eternity. Do not give in to fear or worry, those robbers of abundant living..." p47
As Isaiah 41:13 says, "For I am the LORD, your God, who takes hold of your right hand and says to you, Do not fear; I will help you."