Replying in threads

I have been replying in threads for some time now. I just recently started to use the quote option which makes exchanging ideas easier to do and understand. However, I've noticed when my post gets too long, coupled with cutting and pasting quoteds, going back and forth from the last post to what I am writing makes the cursor in my reply jump all over the place. When the reply is long enough that there is that scroll bar thing on the right, I can no longer add quotes, it becomes quite impossible. Am I doing anything wrong? Do people understand this question? I always press quick reply and also have no smily thingies on the right, though occasionally it pops up for no apparent reason. Perhaps I just need a simpler way to quote. I have been on this forum for years but it's certain technical aspects still have me baffled.