There is an e-text here at Enotes that has the modern English equivalent of each line, and the student may easily have access to this explanation by clicking on the link below. For, this format for answering student questions does not afford enough space for lengthy explanations.
In an effort to assist the student with understanding Act II, Scene 6, here is some explanation:
This scene concludes the subplot of Jessica and Lorenzo's elopement as Shylock has departed for dinner with Antonio, and Lorenzo arrives. As the scene opens, Gratiano and Salerio, friends of Lorenzo wait for him under a shelter; they are surprised that he is late because lovers are normally so excited that they arrive early to meet their beloveds. This is the point of Gratiano's monologue in lines 8-19. In these lines, he draws analogies to other situations. asking when has another repeated the excitement he/she feels for the "firsts." For example, is not someone more eager to sit down to eat than when he rises from the table; is not a horse more interested in a new path than going down one he has traveled before. All things, Gatiano concludes, more exciting when they are sought than after they are experienced.
....Who riseth from a feastWith that keen appetite that he sits down?Where is the horse that doth untread againHis tedious measures with the unbated fireThat he did pace them first? All things that are,Are with more spirit chasèd than enjoyed. (2.6.8-13)
For I am much ashamed of my exchange [of clothes]
But love is blind, and lovers cannot see
The pretty follies that themselves commit,
For if they could, Cupid himself would blush
To see me thus transformed to a boy. (2.6.35-39)
No masque tonight. The wind is come about.
Bassanio presently will go aboard.
I have sent twenty out to seek for you. (2.6.64-66)
I desire no more delightThan to be under sail and gone tonight. (2.6.66-67)