“Fold it yourself!”
You just finished doing a load of laundry. Your live-in boyfriend comments that you need to fold the clothes quickly or else they'll get wrinkled. You're annoyed that he expects you to fold the laundry instead of helping, so you say this.
Fold it yourself!
After you wash and dry your clothes and other laundry, you fold them and put them away.
You can use the word "fold" for "clothes", or for "laundry". Notice that "clothes" is plural, but "laundry" is singular. So in the example above, if the boyfriend said:
You should fold those clothes quickly.
...then the correct response would be:
Fold them yourself!
When you tell someone "___ yourself!" you're saying that they should do it, not you or someone else:
A: Clean up that mess!
B: Clean it up yourself.
If you want something done right, you have to do it yourself.
You can also use "yourself", "myself", "herself", etc. in questions and descriptions:
Are you sure that's what happened? Did you see it yourself?
A: Your hair looks great. Did you get it colored?
Notice that "___ yourself" is different from "___ by yourself". Doing something "by yourself" means doing it without other people helping or joining you:
Sometimes I like to go out to see a movie by myself.
Eating lunch by yourself in middle school or high school is really sad and embarrassing.
I recorded the album myself, but I didn't do it completely by myself. I got some help from Ronnie and a friend of his who's worked at a recording studio.