In the poem "Heart! We will forget him," the heart takes the lead here and has to do with the signficance of warmth and light—true?

In Emily Dickinson's short poem, "Heart! We will forget
him," the speaker uses an apostrophe, speaking directly to her heart. And she also
personifies her heart as something that will, with her, forget him. (Hearts don't have
minds with which to forget.)

According to Dr. L. Kip
Wheeler:

Not
to be confused with the punctuation mark, [an] apostrophe
is the act of addressing some abstraction or personification that is not physically
present: For instance, John Donne commands, "Oh, Death, be not
proud."

At the same time,
personification is:

readability="15">

A trope in which
abstractions, animals, ideas, and inanimate objects are given human character, traits,
abilities, or reactions. Personification is particularly common in poetry, but it
appears in nearly all types of artful writing. [E.g., The wind
howled through the
park.]

The speaker talks
directly to her heart. Between them—her mind and her heart—they will endeavor to forget
"him," perhaps someone who has broken her/their heart. She tells her heart to forget the
warmth he gave to her; warmth may be the comfort and pampered
feelings she had (at one point) when he was around.

readability="9">

HEART, we will forget
him!

You and I, to-night!

You
may forget the warmth he gave,

I will forget the
light.

The speaker notes that
she will work hard to forget the light. This may allude to the
sense that in a dark world lacking in love, that his presence, his
love provided a beacon, a lighted signal with which to navigate her
way.

Emily Dickinson often offers some bit of a surprise in
her poems: something playful. Her heart wants to forget his warmth. The speaker is
trying, also, perhaps led by the heart, to dismiss the memory of
his light from her life.

readability="9">

When you have done, pray tell
me,

That I my thoughts may
dim;

However, the speaker
cautions the heart to tell her when the heart is through so there is no gap in time.
Here the speaker implies that she may not be terribly strong: perhaps she is unwilling
in trying to forget that light. Here comes the playful
twist:

Haste!
lest while you're lagging,

I may remember
him!

She says that if the
heart lags behind too long, the speaker may not be able to stick with her resolve to
forget the light, and may actually remember him regardless of their plan. It seems that
she may still love "him" and being trying hard to get over him: with no guarantee of
success.