So are you to my thoughts as food to life,(1)
The speaker begins the poem with some pretty thoughts about love. Like, come on, if somebody told you that their thoughts needed you the way life needs food, you'd probably feel pretty flattered, wouldn't you?
Or as sweet seasoned show'rs are to the ground;(2)
Pretty much the same goes for line 2 and line 1. If anything, line 2 makes the speaker's feelings of love seem all the more sweet and romantic—not only because he literally puts the word "sweet" in there, but also because the emotions are all wrapped up in a pretty package of nature imagery. Once again, we think if "you" were the person being addressed in this way, you'd feel pretty darn good.
And for the peace of you I hold such strife,As 'twixt a miser and his wealth is found(3-4)
Okay, so the speaker is changing things up a bit, moving from more pleasant imagery to imagery of anguished longing. But maybe that's just even more romantic, isn't it? Just think of all the love songs you've heard, where the singer tells about how he or she is simply dying for your love? We're definitely putting lines 3-4 in the romantic flattery column.