The vivacious Upper East sider vows to save herself in her new relationship with her professor — will she be able to do it?

It looks like Serena van der Woodsen (Blake Lively) may be writing checks she can’t cash — she is vowing to not have sex on tonight’s episode of Gossip Girl! Having recently started a relationship with her professor, and neighbor, the vivacious blond promises to take things slow so they don’t get complicated. Do we really think she can do this?

We will also get to see Blair (Leighton Meester) celebrate her birthday and an appearance from super stylish guest star Rachel Zoe! Be sure to tune in at 9 pm tonight on the CW to catch all the action!