Analysis of I do but ask that you be always fair

I do but ask that you be always fair
That I forever may continue kind;
Knowing me what I am, you should not dare
To lapse from beauty ever, nor seek to bind
My alterable mood with lesser cords;
Weeping and such soft matters must invite
To further vagrancy; and bitter words
Chafe soon to irremediable flight,
Wherefore I pray you if you love me dearly,
Less dear to hold me than your own bright charms,
Whence it may fall that until death, or nearly,
I shall not move to struggle from your arms:
Fade if you must,--I would but bid you be
Like the sweet year, doing all things graciously.