How we cite our quotes:
Now counting best to be with you alone,
Then bettered that the world may see my pleasure; (7-8)
These lines express indecisiveness. The speaker can't decide which he prefers: being alone with his beloved, or flaunting his beloved in public. Doesn't the poem as a whole make it seem likely that the speaker could just as well have added a third line here saying, "Oh wait, actually, I think it's better to be with you alone"? We at Shmoop sure think so. And when you can't settle on any one way of being, dissatisfaction is the inevitable result.
Sometime all full with feasting on your sight,
And by and by clean starvèd for a look; (9-10)
These lines convey essentially the same idea as lines 7-8. By constantly wavering between two options, the speaker makes himself unable to be satisfied.
Possessing or pursuing no delight
Save what is had or must from you be took. (11-12)
These lines suggest the root of the speaker's dissatisfaction. If the speaker has to "pursue" the "delight" he gets from "you," and if some of that delight "must from you be took," maybe his beloved doesn't really like him that much after all. It's gotta be darn hard to be satisfied with being in love with somebody who doesn't love you back.