New York law imposes a duty on landlords to mitigate damages if a tenant breaks a lease. This means the landlord must make reasonable efforts to re-rent the apartment. You may not automatically owe the full remaining rent if the landlord fails to try and find a new tenant. The enforceability of such clauses can be complex and depends on the specific circumstances. Consulting with The Kugel Law Firm can help you understand your obligations and potential defenses.