switching from Lexapro (escitalopram) to Citalopram (Celexa generic)

I was very sleepy a few days ago and told my sister that I thought it was changing drugs. I was so sleepy that people at church was teasing me about trying to stay awake for the sermon. I made a prayer request on our prayer chain for the energy to get through the day. Is that just the side-effects of starting citalopram? I have also noticed that I have argued with my mind about making mistakes at work more than I did on Lexapro. Lexapro seemed to quiet my strange negative thinking quirk better than citalopram has so far. Will Citalopram get better as I continue to take it like Lexapro did? I know that AD tend to take a while to get the full benefit of the drug but is that true when a person switches from a very closely related drug to another?
I have been happy for the past two days. I hope it lasts.