Use
• for emphasis
I myself would never do that!
I painted it myself
I'm not fond of shellfish myself
• reflexively ie when referring back to the person performing the action
I've hurt myself
I spilt coffee on myself
I cried myself to sleep
Note that in all the examples an "I" precedes "myself".
With that rule in mind, it is easy to spot MISTAKES such as:-
Please call John or myself for further information.Never start a sentence with "Myself"
It should be: Please call John or me …
eg Myself and a friend went to Brazil.
It should be: I and a friend… or A friend and I…
Examples
You look pleased with yourself.
One must take care of oneself.
The militants themselves said …
Animals protect themselves from predators
The Queen admired a portrait of herself.