Next time this scenario happens, try something a little different. Ask the child what they are going to do for you and then be their sports commentator!
"Now, ladies and gentlemen, Ms. Lucy Lane is going to attempt to ride her bike all the way to the end of the street and back. Her entire bike-riding career has been leading up to this moment. Let's watch.
"Here she goes! She has such control as she works the pedals with ease. What grace, what precision and speed as she makes the final turn! Here she comes! She has done it! Lucy Lane has ridden to the end of the street and back!!!"
(hold up pretend microphone to Lucy)
"Tell me Lucy, how did that feel?"
(giggles) "Umm, good!"
"Well it sure felt good to watch you! It looked like that final turn might have been a difficult one, but you handled it well. Were you worried about it going in?"
(more giggles) "Umm, no!"
"That is good to hear. I can see that your confidence is what really gives you an edge and makes you a true cycling superstar. Congratulations on your incredible accomplishment today!"
What a great and fun way to be supportive and boost your child's confidence (and of course, be a little bit silly at the same time)!