In Sonnet 75, Shakespeare portrays love as an emotion of extremes, neither of which is too pretty. The way this poem presents it, if you don't have the love you're seeking, it can torment you and make you feel like you're starving. (Boo.) But, because you're so starving, once you finally get it, the emotion can be so overpowering that you wish it would just quit. (Double boo.) To illustrate his idea of a lover, Shakespeare uses metaphors drawn from two other extreme lifestyles: that of a miser and that of a glutton. Neither a miser nor a glutton can properly enjoy the object of their interest: money and food, respectively. Each of them would do much better if he (or she) could find some happy medium.
Lines 11 and 12 suggest that the person the speaker is talking to may not return his affections. This lack of harmony in the relationship might be the root of all the other problems. Sad.
Even if this is a love poem, it portrays love as happening in cycles that are more associated with lust than romantic love. Nice try, though.