That your lease has a damage clause does not mean you have to pay the landlord for rent of entire five years. For tenancy for years, like yours, if you breach, you normally would have to compensate for the entire term. However, modern law, contract or property, require the landlord to use good faith effort to mitigate. Let's say if he finds another tenant, you only need to pay for the difference of rent.
You have three choices. One, give him a written surrender, upon which the landlord must mitigate. Second, assign the lease to somebody and try to get a novation from the landlord. Third, sublease it to somebody else and reserve a remainder.