Glycine is somewhat a double edged sword. On the one hand it acts as an inhibitory neurotransmitter in the suprachiasmatic nucleus, where it helps modulate the circadian clock’s activity: lowers body temp, increases melatonin release, etc. it prepares the body for sleep. It's also the primary inhibitory neurotransmitter in the spinal cord, and much of it's sedating properties come from this MOA.
However, it's also an NMDA co agonist, meaning, it increases excitatory neurotransmission, and it feels surprisingly dopaminergic. It's particularly mentally stabilizing (part of the reason why it's helpful for schizophrenia) but it can get a bit much with prolonged use, especially as the body adapts to it's inhibitory properties, ie. the initial drowsiness fades away. When that happens, your sleep will be cut short to about 4h upon which sleep will be very difficult. The 4h of sleep will feel more like 5 to 6, but alas, it wont be enough and you'll have to cut short the glycine use. YMMV ofc.
Alas, glycine also doesn't work for prolonged use.
With aas you want to lower the "ON" feeling and lower the excitatory HPA axis modulation. In other words, you need to focus on being chill and not directly on sleep. You should learn to listen to your body and mind so you'll know at which point of mental activation you wont be able to sleep. But keeping aas dosages at a reasonable level is the first step.