In Act I, Macbeth is still very much a puppet of Lady Macbeth's desires and ambitions. He is very unsure about this plot his wife has created to murder King Duncan, so he may take over the crown. Having no ill-will toward the king, he is wavering in his resolve and to put it bluntly "getting cold feet". The use of euphemism demonstrates that Macbeth is unable and unwilling to face up to the true horror surrounding this murder. The horror of the impending murder is heightened byt the fact that Macbeth is"his kinsman and his subject,strong both against the deed; then as his host who should against his murder shut the door, not bear the knife myself (himself)" (I.vii.13-16). Macbeth has multiple ties to the king that demand that he honor and protect him, not murder him!
All very good. One final thought -- Macbeth is weak. From start to finish, Macbeth is weak. He grows more forceful and sudden in action, but he is just a insecure and bumbling idiot. This play was written just after James I took the throne of England, and Macbeth is a representation of James --- a man who speaks poorly, is weak in thought and constitution, and is considered at the time (in comparison with Elizabeth) a poor ruler for the country.
That is a very good answer!
I thought I might add an interesting point that merely conforms with what you have said as a sideline illustration.
In Act IV scene I the witches describe what they do as –a deed without a name-
In his soliloquies prior to Duncans murder Macbeth refers to the act in much the same way. He uses the word do rather than name the deed.
-If it were done, when tis done, then twere well / It were done quickly (I.vii.1-2)-
-I go and it is done (II.i.62)-
Done is a funny word in Shakespeare as it usually refers to sex, equalising the act of murder with consummation.
Elsewhere the deed is it… Macbeth speaks the forbidden word but once
-My thought, whose murther yet is still fantastical-
And this is equivocation, while admitting he is thinking of murder he also suggests that thought itself is murdered.
Throughout Macbeth dialogue dwells obsessively on the unnameable, both action and identity are lost in the confounded language of the play.
Read- Shakespeare: Violation and Identity, by Alexander Leggatt for more detail