Act 3, Sc. 2, lines 161-186: What is the purpose of this scene?

Player Queen. And as my love is sized, my fear is so.

Where love is great, the littlest doubts are fear;

Where little fears grow great, great love grows there.

Player King. Faith, I must leave thee, love, and shortly too:

My operant powers their functions leave to do;

And thou shalt live in this fair world behind,

Honoured, beloved; and haply one as kind

For husband shalt thou -

Player Queen. O confound the rest.

Such love must needs be treason in my breast.

In second husband let me be accurst;

None wed the second but who killed the first.

Hamlet. [aside] That's wormwood.

Player Queen. The instances that second marriage move

Are base respects of thrift, but none of love.

A second time I kill my husband dead,

When second husband kisses me in bed.

Player King. I do believe you think what now you speak;

But what we do determine, oft we break.

Purpose is but the slave to memory,

Of violent birth but poor validity,

Which now, the fruit unripe, stick on the tree,

But fall unshaken when they mellow be.

Most necessary 'tis that we forget

To pay ourselves what to ourselves is debt.

What to ourselves in passion we propose,...