When Sir Philip Sidney was at Frankfort, he was advised by the celebrated printer Languet in the midst of his studies not to neglect his health, “lest he should resemble a traveler who, during a long journey, attends to himself, but not to his horse.” The body may indeed be well likened to a horse, and the mind to its rider; for the one is the vehicle of the other, and whatever be the object of the journey, whether to perform the most generous actions, or engage in the most patriotic enterprises, the animal will sink under excessive labor or inadequate nutrition; there being only this important difference, that with the horse the rider sinks also, as their existence cannot be separated without death.

参考译文：菲利普·西德尼先生在法兰克福学习期间，著名的印刷商朗凯建议他不要忽视健康：“这样你就不会像一个旅行家一样，在长途跋涉中，照料的是他自己而不是他的马。”人的身体也许可以被非常贴切地比喻为马，人的思想则可被比作骑马人。因为马匹是骑马人的交通工具，无论旅行的目的地在哪里，无论是要体现最慷慨的壮举，还是致力于最高程度的爱国事业，在高强度的劳作下或者是缺乏营养的情况下，动物将会无一例外地垮掉，而一个非常重要的不同之处在于，马匹垮掉后，人也会跟着摔下来，因为他们是相辅相成、共存共生的。
 
请教曹老师，
1．lest he should resemble a traveler… 中should是什么意思？
2.  whatever be the object of the journey, 为什么不是whatever the object of the journey is ？
3. there being only this important difference, that …... 是什么成分？
谢谢老师。