Advice needed - getting from sweater to bag

The tale of my sweater

Sung to the tune of "I had a poor meatball":

I had a warm sweater, all covered in shapes,
I lost my warm sweater when it develop-ed gapes.

I'd wear it to parties, I'd wear it to school,
But then my poor sweater weren't worn at all.

I'll fling it aside now, and wash it on hot,
And soon my warm sweater will be changed a lot.

One day my warm sweater will be a felt bag,
But how do I wash it, so it doesn't snag?

This is my problem, what on Earth should I do,
Should I leave it in one piece or sleeves cut off two?

My sweaters worn out now, and I am so sad,
But when it is felted, then I will be glad.