Great answers here, all.

With my songs in the Fundamentals Course, do your best, but feel free to move on.

Your skills are still in the process of developing, and that just takes time. 

You can always circle back to a song later on if you want to try to bring it up a notch or two. 

The songs I wrote for Guitar Fundamentals were meant to give "real-world" context to the chord-lessons we had just done.

It doesn't mean you have to learn to play all the songs well as you are going through the course - just do your best, and notice how each one encompasses some new skills or concepts you just learned in previous lessons. 

Also, keep in mind that you can slow them down to make them easier to practice with.

Have fun!  -Lisa