The speaker describes his emotional attachment to the beloved as both sustenance and torment, oscillating between satiation and starvation.
Sonnet 75 presents obsessive love as a state of perpetual swing. The speaker cannot achieve equilibrium. The quatrains alternate between states ('proud...and anon,' 'Sometime...and by and by') and the couplet collapses these oscillations into a binary: 'all' or 'away.' There is no middle position, no contentment with moderate love. This reflects the psychological structure of anxious attachment: the beloved is simultaneously the solution and the threat. Possession brings anxiety (what if they leave?), and separation brings craving. The speaker is trapped in a feedback loop where neither satisfaction nor deprivation resolves the underlying insecurity. Love has become pathological.
The miser metaphor (line 4) is not incidental—it defines the speaker's entire relationship. The miser loves wealth but is enslaved by it. Similarly, the speaker's love for the beloved creates constant fear of loss. The beloved is 'treasure,' which makes them simultaneously precious and vulnerable to theft. By investing all emotional worth in one person, the speaker makes that person an obsession rather than a love. Lines 7-8 reveal this further: the question is not what makes the speaker happy but whether to hide the beloved or display them, whether to keep the 'treasure' private or public. The beloved has become an object of conquest and display, not mutual regard. The sonnet thus documents the corruption of love into possession.
A person who bases their entire emotional equilibrium on another. If the beloved is present and attentive, the speaker feels overfull; if absent or withdrawn, they feel starved. There's no middle ground. This is the pathology of anxious attachment: the other person becomes simultaneously all food and all threat, and the relationship oscillates between obsessive closeness and paranoid fear of abandonment. It's love as addiction, not reciprocal bond.