Difficulty Sleeping After WBTB

I've been practicing WBTB for a while now, and it's given me very good results - always a vivid dream or two that I can remember in full. However, I have high difficulty falling asleep after performing a WBTB.

Normally, when I go to bed, it doesn't take that long. Whenever I WBTB, it takes much longer to do such. I only stay up for a WBTB for about 5-10 minutes, then slink back to bed.

I'd rather not stop using WBTB, not after it's given me fantastic results so far. So I ask: What can I do to help me fall back asleep after a WBTB? Should I do somehting different with the time I spend performing the WBTB (When I WBTB, I do all mantras, RCs, and try to visualize a dream before going back to bed)?

First you want to identify if what might be causing the difficulty. Then experiment with solutions. There might not be a specific cause, but that's the first thing to check. Some causes might be:

too much light
too much activity
alarm is disruptive (best to wake naturally without alarm)
too late or too early in sleep cycle
distracting thoughts (often about what you need to do the next morning)
discomfort or distraction in the room (cold temperature, pet, etc.)
supplements

Next, do you feel sleepy? Don't force yourself to lay down unless your feel sleepy. It sounds counter-intuitive but you might want to stay awake longer and let the urge to sleep to get stronger. Instead of begin alert for 5 minutes and struggling to sleep for 15 minutes, stay up for 15 minutes and you might fall asleep in 5 minutes. You can read, meditate, or do breathwork to extend the time. Anything as long as it's relaxing and doesn't expose you to too much light.

Going back to sleep in the middle of the night's sleep cycles can take longer than going to sleep at bedtime. People vary greatly in terms of back-to-sleep time. I personally tend to become awake very quickly, even without any mental activity and being careful to avoid light. I've read about and developed a few techniques for falling to sleep that work for me. Some of these which work for me include:

+ focus on relaxation, don't "try to sleep", and especially don't think "oh my God if I don't get back to sleep I'm missing a bunch of dream time!" which is guaranteed to keep you up for hours
+ release all tension in the body (breathing exercises, tense/relax), especially forehead/cheeks/jaw
+ unfocus your eyes (you can carry tension in your eyes looking at the backs of your eyelids, trying to focus on the imagery)
+ let thoughts which arise pass through your mind and exit (don't try to force them out)
+ try to "unclench" your mind, so that it's not holding on to anything

You can do all of this sitting in a chair, and move to bed only when you start nodding off. Many "how to sleep" guides say don't get into bed without being sleepy first (as sisyphus wrote), and if you can't fall asleep within some time (10-20 minutes) get out of bed again. You want to associate bed with sleep/dreaming, not with tossing and turning and alertness. I have personally not done this yet (getting out of bed if I can't fall asleep in a certain time), but I still take a long time to get to sleep sometimes, so maybe I should!

On the other hand, I've had a bunch of lucids recently that came after 2 hours of trying to get back to sleep :). One of the absolutely most consistent things you'll hear from lucid dreamers is that WBTB produces more LDs. So don't grudge that awake time, you can do dream incubation, more mantras, or just practice your falling back to sleep technique. Yeah you might lose some sleep, but if you get LDs, it'll be worth it :).

Also tailor your WBTB times (start times and time awake) to yourself. Find out what works best for you, and stick with it. That can take time but it's also worth it.