、。
You can start loving freely, but ending a love is a different matter.
Literal
Romantic-love [topic-は] freely can-be-started, romantic-love [object-を] to-end [as-for-には] it-doesn't-go-that-way.
そうはいかない is an important idiomatic set phrase — literally 'it doesn't go that way (as-for),' meaning 'it's not that simple,' 'things don't work that way.' Often follows a clause setting up the expectation. The には after 終わらせる is composite: に (goal/purpose) + は (contrastive topic) — 'as for ending it.' The causative 終わらせる ('cause to end, bring to an end') is used because 終わる is intransitive.