When the subject and the object of the verb is the same person or thing, we use a reflexive pronoun.
In the given sentence the subject and the object of the verb is 'I'.
The reflexive pronoun for singular first person 'I' is 'myself'.
Thus option D is the correct answer.
The reflexive pronoun for singular third person is 'himself','herself' or 'itself' according to the gender of the noun. Thus option A is incorrect.
'Themselves' is the reflexive pronouns for the plural third person. Thus option C is incorrect.
The reflexive pronoun for singular second person is 'yourself'. Thus option B is also incorrect.