We use reflexive pronouns in 3 cases:
1: When the subject and object is the same.
- He talks to himself a lot.
- You’ll hurt yourself.
- I can’t make myself believe it.
2: When we want to emphasise that the subject was the only actor.
- If you want a job doing properly, do it yourself.
- He washed the car himself.
- I had to pay for everything myself.
3: After ‘by’ to mean ‘alone’
- I saw a little boy playing by himself.
- She lives by herself
- I don’t want to be all by myself anymore!