How do I slow down my heart rate and relax?

I'm not really new to the whole concept of lucid dreaming, and in fact I had started some sort of dream journal to start dream recall; but school got in the way and it's hard to commit to writing down your dreams while waking up at 5:30 every morning. I've been trying to develop that, however, during the past couple weeks, but progress seems to come incredibly slowly and I only seem to remember dreams once every 3 or 4 nights.
So until I build up dream recall over a long period of time, or I find a way to do it quickly; I'm stuck with trying to WILD. But every time I attempt this, as I'm relaxing, I notice I'm getting relaxed, I get excited, and my heart rate jumps up to a ridiculous pace. This repeats until I get frustrated and give up.
Everyone I see who is here seems to start having auditory or visual hallucinations fairly quickly; I can't seem to get to that even with several techniques. I get to hypnogogic purple and green images flashing and twirling before my eyes (similar to my experiments with Ganzfelding) and semi-sleep paralysis in my arms/legs, and I'm gone. It's a roadblock for me. If anyone here has had this problem and has found a way to stop it, I would really like to know, because this wouldn't only help me with WILDs, but with regular sleep as well. I seem to be a borderline insomniac.
Thank you,
oddvids

One thing that helps me not particularly with lucid dreaming but just surviving anxiety throughout the day is controlled breathing, I breathe in through nose hold it for one-two seconds and then exhale through my mouth. While I do this I make sure to have my eyes closed and try to imagine myself somewhere relaxing where I know I can't be distracted, such as a mountain top or abandoned beach. I don't know if this will particularly translate into your situation but it just might. Good luck!

If you're breathing deeply and you feel relaxed, the rest of your body will relax as well, including your heart rate. By concentrating on your heart beat, you are amplifying the sensation of the beat, and I know a few people who say that it feels as though your heart is beating out of your chest. Remember that this is purely psychological, and try to concentrate on other things, such as your relaxed and steady breathing.

As has already been said, breathing techniques are a very good way to relax.

Feeling excited and an increased heartbeat is quite common when trying to WILD.
As Telemachus pointed out, this is purely psychological.
Try to focus on something else.
It is often suggested to focus on your breathing, but this is something I personally have a lot of trouble with.
For me, concentrating on breathing is what usually causes this feeling of an insane heartbeat.
I found that for me, the best thing to do is to think of a relaxing scene.
My preferred choice is a beach at dawn, the sound of slowly moving waves, the refreshing salty breeze of air... you get the idea.

Another thing I'd like to add is: try not to focus on or wait for the effects of sleep paralysis. (such as the lead blanket feeling or hallucinations)
Everyone experiences sleep paralysis differently, it's quite random. It can also randomly change every time you enter it.
It's perfectly possible to perform a WILD without experiencing any visual or auditory hallucinations, so don't worry about this too much.

I agree with the breathing advice for relaxing and slowing the heart rate.

In the world there are different sleepers, and no two people fall asleep in the same way. And no two people learn to lucid dream in the same way.
As such, you should not compare your dreaming progress so much to others.

If you are having difficulty to falling asleep,
try and get a early night to bed, and make yourself warm & comfortable.

Also for some researchers - a lack of vitamin B6 causes some people to have difficulty remembering dreams.

As others suggested, take deep, slow, rythmic breaths. And while doing this, concentrate on the heart or at least the feeling of having a heart, these things should slow it down.

Good luck with lucid dreaming.

Thanks for all your help! I tried these suggestions, and I found that I wasn't taking time to relax before attempting to WILD. Working on breathing really helped. Now I'm much closer to completing the WILD.