I've always said street photography is a sport and like any other sport or activity, you have to warm up before you go full throttle. Street photography is no different! The first 30 minutes of your session is simply practice. You have to find your groove and get into the flow of things. My first 30 minutes usually consist of me taking pictures of any subject I see, I don't care if the lighting is good or bad or if the subject isn't amazing, I'm just trying to get rid of any jitters or fear that I may have.
After that I consider myself loosened up. I know what settings my camera should be on and I also have a general idea of what type of image I want to capture. I feel like for that first 30 minutes you're almost desperate to capture something good, but once you kind of settle in you stop chasing photographs and you just let them come to you.
This may not work for everyone, but it is something I think everyone should try. During your next session, get out there and give yourself 30 minutes to warm up, don't make any decisions during those initial 30 minutes... Going home is not an option, the streets don't suck, just spend 30 minutes taking photographs of anything that grabs your attention. After that, began your real session and see if it's any better. Every sport requires you to do some type of practice, some type of stretching... Street photography is no different. Happy shooting!