I usually have long streaks of sleep, but sometimes in them, I'll wake before I completely finish my sleep schedule. Sometimes I have trouble getting back to sleep, and when I do, it's impossible to fall back to sleep. Sometimes even if I'm asleep for 4 hours, I'll feel like I've been sleeping for 12, and will proceed to be tired the rest of the day. Can I ensure that I'll fall back to sleep, even at the end of a sleep cycle?
Yea this is a problem. There are some techniques like auto-suggestion. I heard about one to fall asleep and it's very effective one. You start with your mind at thumbs and let them dissolve into the air and slowly continue higher over legs. Then hands, stomach, chest, neck, head. Just feel like those parts are becoming nothing but air. Like your body is disappearing.
There is also a sister technique. You visualize the same but instead of lightness you feel heaviness. Like those parts of your body are extremely heavy.
Try also to go to bed and leave everything behind. Just clear your mind before going to sleep. Feel relaxed. You should not take your problems to bed.
I would say don't try to fall sleep, more just feel comfortable and happy knowing your body knows what to do, your not in control anyway. See a silly story your mind randomly comes up with or blackness but don't feel attached or even care what happens or if it melts off. I sometimes perform SSILD do it over and over to you get bored or start losing track and then start over again. The more you stress the worse as everyone knows so be comfortable just relaxing, your still getting great benefit like sleep. Like Hitokage said don't take your problems to bed, write them down before bed on paper, leaving them for when you can really attend to them tomorrow. I have also heard but have not tried, you lie on your back maybe on bed, place your feet on the wall with legs bent and relax for 15mins then role round into your bed into your favourite position. It's meant to work with blood around your head or something. But lately SSILD worked for me, i do it can get boring and fall asleep or do it stop drift off after a few minutes.
This is a common question, it deserves a sticky thread. flight is correct, "trying to sleep" is ineffective and produces more insomnia. Simply try to relax completely, mentally and physically, releasing all physical tension from mind and body. Enjoy this relaxed state, and don't look for anything else besides this restful drifting place. If you do this nature will take over and you will sleep. This takes practice, diligence, and determination, as tension can hide in very tricky unexpected places: only you can find them all. It also takes concentration to keep your mind relaxed for the period it takes for you to fall asleep, (but it has to be "soft" concentration).
For me, other than the usual places (jaw), I found that I held tension in my eyes, trying to "look" at my eyelids. I also sometimes have a "clenched mind" feeling when I can't fall asleep: recognizing that and releasing it is key.
Falling asleep when not very drowsy is basically meditation, in the sense that you want to let all thoughts flow right through you: acknowledge them and let them go by. The difference is that the aim is not mindfulness, but total relaxation into sleep, so you don't want to "hold on" to awareness (unless you're trying to WILD, where you're trying to aim for that tiny target that sits somewhere on the shifting border between unconscious sleep and awake awareness)