I've had quite a few LDs over the years but would keep giving up and go for spells without trying because of the same problem. Only fairly recently did I start having long LDs. Because I kept waking up, I got very frustrated and bitter and started to doubt myself. For me, I know it was a mental barrier I had to overcome, knowing that I could do this. Once I had my first really long LD, it's like I proved to myself it was possible and it's been going much better since then.