'You must decide for yourself, and if you consider it more important to
do what his sisters want, than to gain the happiness of being his wife,
I certainly advise you to refuse him.' 去书内
consider it more important A than B(认为A比B更重要),其中: A为to do what his
sisters want(不定式短语,what引导宾语从句作do的宾语); B为to gain the
happiness...(不定式短语,of being his wife为介词短语作后置定语)。