The breakup speech is always difficult to formulate. Depending on the state of your relationship, and whether not you'd actually like to keep that person in your life, some dumpings require more delicate words than others. Sure, there's always the go-to, "I don't think this is working" or "It's not you, it's me" line, but only a daft idiot wouldn't see that as bullshit.
Put a little thought into yours. Demonstrate care. Be creative. Use these break-up lines from movies as inspiration, or just rip them off entirely. Either way, they're a lot more inspired than, "It's over."