Tis now the very witching time of night, When churchyards yawn, and hell itself breathes out Contagion to this world: now could I drink hot blood, And do such bitter business as the day Would quake to look on. Soft! now to my mother. —
Summary Act 3 Scene 2 Solioquy
In this moment Hamlet is in a mood in which he could kill his own mother. But he knows that is just him lashing out and he could not "do such bitter business as this day would quake to look on," meaning he knows he would regret it.