Yeah, it can take quite a long time to take effect; it took a good couple months in my case. Ssri's are obviously not "feel good" drugs, they're great for chronic depression, but they wont make you feel great or anything; you'll still have bad days occasionaly.
One thing about citralopram is it can be quite hard to sleep on it; I had to switch
To mirtazipine, which is a fairly powerful sleep aid (also an appetite enhancer)
So, if you're taking citralopram, just be careful to be patient; don't assume they're not working because you don't feel immediately better. Also, their anti-depressant effects last a long time; a lot of people stop taking them because they don't feel they need them, and then weeks later they end up with chronic depression again.
Also stopping after a long time can give you "ssri discontinuation syndrome" a euphemism for withdrawal symptoms; you can become dependent on ssris.