Beginning, Middle, End

Everything in existence comprises three 'parts': beginning, [Heb.‘rosh’ (lit. head)] - the capacity to receive or initiate a process; a middle, [Heb. ‘toch’ (lit. within)] - the capacity to contain, or to reach the peak of a process; and an end [Heb. ‘sof’ (lit. end)] - the ability to give, or to bring a process to completion. According to Kabbalah, and as echoed by philosophers, this tripartite principle is a recurring pattern in the world, manifest at every level:

When water is poured into a glass; the beginning;
When contained within a glass; the middle;
When poured out of a glass; the end.

The day of Shabbat receives from the six working days preceding it, as taught, 'One that prepares for Shabbat 'eats' on Shabbat'; the beginning;
Shabbat itself, a day of spiritual delight, 'And you shall delight in the Lord...'; the middle;
Shabbat infuses spirituality into the following six working days, as stated, 'From it [Shabbat] all the weekdays are blessed'; the end.

One's ability to study; the beginning
The ability to assimilate and retain information; the middle;
The ability to apply the information in practice; the end.

The upper arm until the elbow; the beginning,
The forearm until the wrist; the middle;
The hand; the end.

The fingers divide into three parts as well, as do the legs, as does the body at large:
the head, the seat of intellect; the beginning;
The torso, where emotion is strongly felt; the middle;
The legs, the medium for action; the end.
                                           
Every skateboarding trick consists of three stages:
Preparation for the trick: correct foot placement, attainment of the right speed to perform the trick, crouching down, etc; the beginning;
The performance of the trick itself: a kick flip, boneless, 50-50 grind, etc; the middle;
The  landing and ride-away: crouching down to absorb impact, etc; the end...