I assume since you have a prescription, you've already talked to your doctor about it a little?
Also, everyone is different and will react differently to medications, so I can only speak for myself, but I was on it for two years. It worked better for me than Paxil, which made me feel like an emotionless shell of a person. If I missed a dose of Effexor though, it made me feel really weird and I'd get unsettling "brain zaps" as they're called. Sex drive was also down a little (though again, not as bad as with Paxil).
After two years I felt like I could cope with my anxiety without being on medication anymore and decided to slowly taper off of it, after talking to my doctor of course. So I took about a month to slowly ween off of it. I would say, besides the 'brain zaps' when I missed a dose (and a little when tapering off at the end), it really helped me. Hopefully though you can also get to the point where you can manage your anxiety without medication. Good luck.