I think the main points where the attempt may fail are:
• If you don't test your setup. This includes anchor point, rope, knots, all materials to be used. You must learn to tie knots properly. And test that your rope and anchor points are strong, that under no circumstances do they give you the feeling that they could break.
Test by putting your setup in the chosen place for the attempt and hang with your hands, applying all your full weight for a while; do this a few times. Everything must remain firm, without any change or damage.
• If you don't choose a private location and anyone finds you, you'll be in trouble.
If they find you before you hang yourself, you could end up in a psychward and under surveillance.
If you are found hanging mid-attempt and are "saved", you could be left with lasting effects. The longer the brain goes without oxygen, the greater the damage will be.
• If you plan attempting Full Suspension, you must ensure you are at a suitable height off the ground. This is because, when you apply your weight, the rope will stretch slightly, and the compression of the ligature on the neck will reduce its diameter, the Arbor Knot tightens to the maximum and penetrates deeply into the neck. So your stand/chair should be at least 50 cm high to ensure your feet don't touch the ground.
• If you plan attempting Partial Hanging, you should choose a suitable position where you can apply as much weight as possible to put enough pressure and compress your arteries.
I believe that in this case, failed attempts are inevitable, until you find a suitable position that allows you to lose consciousness quickly without feeling discomfort or the sensation that "your head is about to explode" due to incorrect compression on the neck.
• Suspicious attitude, any change in your behavior will alert those close to you and you will be under constant supervision.
• The survival instinct, difficult to suppress, is something we have evolved to keep us away from all risks and prevent us from suffering harm.
Mistakes in the Hanging method