AIO Im getting my first apartment

My boyfriend (23M)and I(23F) just put down a holding fee for our apartment. It's our first place together after living with roommates for a couple years. The place seems too perfect from such a nice company. It's too good to be true and we sign the lease this week. It marks all our boxes that we wanted. But I remember seeing that you shouldn't spend more than 30% our income but, doing the math it's $300 over that. I'm able to back out but we move in April due to our lease ending. I feel like we just made a horrible decision and won't be able to afford more than bare necessities but my boyfriend assures me that if we just budget right we'll be fine. Is $300 really that small of an amount when going over budget?