i aint gonna lie
A dramatic way of saying you're going to say something, even though it's probably not true. It's like when you're trying to impress someone but you're just full of crap.
I aint gonna lie, I told my crush I liked them, but I didn't.
I aint gonna lie, I said I was going to get a good grade, but I failed.
I aint gonna lie, I told my friend I was going to be on time, but I was late.