Well two parts
The first is when you first start drugs are an easy way to induce lucidity. However, the farther you get into it, the harder it is to induce drug based lucidity. It's basicly your subconscious looking out for you.
secondly. It doesn't get easier for a long while. It took me months to do it semi regularly. That being maybe once a week, or a few times if I napped a lot. And much longer for whenever I wanted to. Even now, I plan my sleep schedule for when I want to have lucid dreams and I've scheduled my classes around them. But I've also been a avid learner. With my study of mysticism and want to know and excel it took me a much shorter time than most people can hope for. The biggest thing to remember is to not get discouraged.