Yes and no, a scale can help by telling if you are losing or gaining weight but the downside is that it can also discourage you. It can make you feel like you are not making any progress at all or it can make you feel like you have gained weight.
Lady Macbeth influenced Macbeth's decision to murder Duncan by being manipulative and questioning Macbeth's status as a man. She claimed that she would have "plucked the boneless gums out of her nipple" if she had promised it to Macbeth. This prompts Macbeth to follow through with his promise when he said he would murder Duncan earlier.
She asks him if he would rather be a coward than seize an opportunity to achieve the "ornament" of life - the crown. Additionally, Lady Macbeth says that she cannot love a man who is not willing to have the integrity to do such a thing, this really persuades him as they do share a passionate bond throughout the play.
Hope I helped!
