'To forget one's self' definitions:

Definition of 'To forget one's self'

From: GCIDE

Forget \For*get"\, v. t. [imp. Forgot(Forgat, Obs.); p. p. Forgotten, Forgot; p. pr. & vb. n. Forgetting.] [OE. forgeten, foryeten, AS. forgietan, forgitan; pref. for- + gietan, gitan (only in comp.), to get; cf. D. vergeten, G. vergessen, Sw. f["o]rg[aum]ta, Dan. forgiette. See For-, and Get, v. t.]
1. To lose the remembrance of; to let go from the memory; to cease to have in mind; not to think of; also, to lose the power of; to cease from doing. [1913 Webster]
Bless the Lord, O my soul, and forget not all his benefits. --Ps. ciii. 2. [1913 Webster]
Let my right hand forget her cunning. --Ps. cxxxvii. 5. [1913 Webster]
Hath thy knee forget to bow? --Shak. [1913 Webster]
2. To treat with inattention or disregard; to slight; to neglect. [1913 Webster]
Can a woman forget her sucking child? . . . Yes, they may forget, yet will I not forget thee. --Is. xlix. 15. [1913 Webster]
To forget one's self. (a) To become unmindful of one's own personality; to be lost in thought. (b) To be entirely unselfish. (c) To be guilty of what is unworthy of one; to lose one's dignity, temper, or self-control. [1913 Webster]