Pronouns ending in -self or -selves, as you indicate, Paolo, are reflexive pronouns. Verbs which are reflexive in many languages are not normally reflexive in English. Thus, we would say:

• My beard growth is so strong that I have to shave twice a day. (Not: shave myself?
• Remember to wash behind your ears. (Not: wash yourselves?
• The door opened and the Queen walked in. (Not: opened itself?
• He is interested in stamp collecting. (Not: he interests himself?

However, if it is necessary to make it clear who is responsible for the action, reflexive pronouns may be used:

• After the stroke, he is quite paralysed down his left side and unable to dress himself.
• Somebody has to come in to dress him.

Reflexive pronouns usually refer back to the subject of the clause and are used to talk about action where the subject and object are the same person. Study the following:

• Jamie was in such a hurry that he cut himself shaving this morning. (Not: cut me?
• She decided to end her life and killed herself by swallowing rat poison.
• I must get myself a new pair of trainers. These are falling apart.
• Nobody offered to serve Kevin so he helped himself to the vegetables. (he = Kevin himself)
• Nobody offered to serve Kevin so he helped him to the vegetables. (he = somebody else)
• They missed the ferry by five minutes and only had themselves to blame.

-self / -selves for emphasis

We sometimes use reflexive pronouns to emphasise the subject or object when we want to draw attention to that person or thing. When the reflexive pronoun emphasises the subject, it is more usual to place it at the end of the clause rather than immediately after the subject itself, though both positions are possible. Study the following:

• We ourselves prepared and cooked the five-course meal. Nobody helped us.
• We prepared and cooked the five-course meal ourselves. Nobody helped us.
• You yourself won't be expected to attend the meeting, though your deputy will be.
• You won't be expected to attend the meeting yourself, though your deputy will be I'll go and see the Director-General himself if those rumours about redundancies are true.
• What wonderful soup! Did you make it yourself?

By oneself / on one's own

By oneself is often used as an alternative to on one's own. Both have two meanings, either 'without company' or 'without help'. Compare the following:

• She's left the flat and is living by herself. She says she's always wanted to be on her own.
• Don't help him to cut up his food. He's seven now. Let him do it by himself. He can do it on his own.

-selves and one another / each other

Take care not to confuse reflexive pronouns and each other / one another. Compare the following:

• They saw themselves in the mirror. (Each of them saw himself / herself)
• They saw each other at the theatre. (They bumped into one another)

fixed expressions with -self / -selves

Do you know all of the following expressions? They all make use of an imperative for instructions/suggestions where the subject is implied.

• Enjoy yourselves! ( said to friends / relations when they are leaving you)
• Behave yourselves! ( said to children when they are leaving you)
• Help yourself! ( said to a guest when you are offering him/her food or drink or other facilities in your home)
• Come in. Make yourself at home! ( said when a guest arrives at your house)