Sweet love, renew thy force; be it not said
Thy edge should blunter be than appetite,
Which but to-day by feeding is allayed,
To-morrow sharpened in his former might:
The poet laments,  personifies  and addresses the emotional force of love, pleading for it to reinvigorate him. The biochemical phenomenon of being “in love” is one that peaks but eventually fades over time. Shakespeare experiences this emotional decline and is saddened. 
 The technique whereby a poet addresses something inanimate —  an object or an idea — is known as  apostrophe  — ( not the punctuation mark) — one of the most famous of which is Keats’s  Ode on a Grecian Urn .
Sonnet 56