Leaking out of energy is a general error among Taiji learners. It occurs in many places and happens quite often.
This is quite difficult to explain. Let me use an example and imagine the following scenario:.
The gun powder from a bullet is emptied into a little heap on the floor of a large room. A lighted match is applied to it. Poof! It burns up with a flash and some smoke, but not much really happens. If that same (intact) bullet was placed into the chamber of the gun it was made for and fired, it posesses a lot of power for destruction!
Why? The answer is very simple. The spilled powder on the floor creates energy that leaks in all directions. The powder in the bullet creates power that is controlled by the bullet casing and gun barrel. The leaking can only occur through a guided hole and direction.
The ancient weapon of bow and arrow are also good examples of such device. Energy is controlled and guided for a purpose.
Our body is more complex than the bow and arrow, and more complex than the gun and a bullet. However, the complexity also poses a problem. It is more difficult to control the energy on the body.
When we practice Taijiquan we must use our energy like the energy in a bullet. What does this mean? First, it means we must follow the proper way specified in the routines for movement. In this sense, the learning and training of routines (Such as Yilu and Cannon Fist) are called making the train track, learning the rules, learning how to move energy, setting the alignment, and other such names. They all refer to the same thing: learning how to control and manipulate energy.
A taiji form/routine is not designed to make you look nice. It is not designed to make you feel good. It is designed to train your body to become a device that controls and guides the energy in your body.