I used to
Now I only do it if I'm injecting something that would be really bad if it got into a vein, or if I'm site injecting (which I almost never do)...I can actually kind of feel it when I do thigh injections it's strange, I don't really aspirate, but sometimes it doesn;t feel right and I take the needle out and there's blood and I just do it again....But it is a good idea, it's just after you inject so many times you get lazy...the first timne I injected I was trembling, and nervous, now I don;t even think about it. Hopefuly if you;re injecting into a vein you could feel it and stop before you injected too much.