Reflexive pronouns (myself, yourself, himself, etc.) may be accented or not depending on their function. They are mainly used in too different ways.
Firstly, as true reflexives, that is, when the subject and the object are the same person, or also after a preposition. In this case, they are not accented.
(314) 
He was shaving and cut himself.
(315) She’s always so proud of herself.
The second use is for emphasis, in which case they are stressed. If they happen to be at the end of the IP, therefore, they take the tonic.
(316) I don’t want you to spoil it. I’ll do it myself.
(317) They built their house themselves.
Of course true reflexives can be emphatic too. Then they are accented. Let’s compare these two examples:
(318) She wanted to have a grounding in grammar, so she bought a book and taught herself.
(319) I’ve never learned anything from you. Sadly I had to teach myself.
Here are different speakers using reflexive pronouns in all the aforementioned ways:
(320) I would’ve crippled myself, spiritually, if I’d left (Richard Flanagan; Tasmania, Australia).
(321) People renaming themselves (Roddy Doyle; Dalkey, Ireland).
(322) We started with the decision to cut out the middleman and sell the work himself (Mark Lawson; London, UK).
(323) And the idea of social exclusion is that you could exclude yourself (Owen Jones; Sheffield, South Yorkshire, UK).
(324) I set out knowing that I was sort of making a double album, and I kept it to myself (Elvis Costello; London, UK).
(320) and (321) are instances of true reflexive unaccented pronouns. In the other three examples the pronouns are used emphatically. It is worth noting that in (323) the subject and the object are the same and in (324) the pronoun comes after a preposition.