I find conservation of energy and linear momentum to be quite natural to understand, but I find conservation of angular momentum really, really tricky. Let me give two examples: (a) I call my system as a stick with identical springs at its ends, facing opposite directions, each spring is coiled with an identical marble. The whole system is at rest, and the origin of my system of coordinates is the center of the stick. Therefore at T=0s my total linear momentum and angular momentum are both zero. Then at T=1s the springs release, shooting out the marbles at opposite directions, and the stick starts to spin. The total linear momentum is still 0, but while the total angular momentum around origin of the two marbles is zero (they cancel each other), the stick is spinning and will have a non-zero angular momentum, so the total angular momentum of my system is now non-zero. There were no external forces or torques... I can't understand how there can be any conservation of angular momentum if I applied no external forces or torques to my system, and now the thing is spinning... (b) I call my system a slightly asymmetrical cloud of gas at rest around its center of gravity, with no rotations. Total angular momentum is zero. Gravity starts to do its thing, and the cloud starts to collapse to its center of gravity, but the thing is slightly asymmetrical, so the collapse is not perfect - it will start to have differences in speed, which, for being a gas, will eventually cause the thing to rotate. At some point the cloud of gas is collapsing and rotating towards its center of mass, until it forms an excellent rotating disk on its way to making a star. The direction of rotation will somehow depend on these initial irregularities, but whatever it is, now the system has a non-zero angular momentum. But there were no external forces, just internal force of gravity. In both cases total linear momentum was conserved and total energy was conserved, but angular momentum was not conserved even if there were no external forces or torque... what am I missing here?