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Patience and luck.
There are many much more skilled than myself at this.

I don't think I would have the patience for this! I'm sure its an amazing skill to have though! I will give it one go when I am next on a beach and see how long my patience lasts me!

It can be sort of a relaxation technique.
You have to concentrate and it helps take your mind away from other crap, at least for the moment.

Yes I can imagine, and yes you must need a lot of concentration!!