In chemistry, there are atoms or molecules that can react very strongly with one another, perhaps leading to a new molecule, or to a release of energy.
Yet, these particles may not react, unless they have a sufficient energy, the "activation energy".
The activation energy is like a fence to climb over before you can ski down a hill. Often times, the reactions don't happen in our lives, because we do not climb over the fence, we do not reach the activation energy.
Some reasons for the activation energy phenomenon may be that some particles need to be "pushed together" energetically in order to react. You may need to push yourself sometimes into an action that ends up being extremely meaningful and self-sustaining.
Other reasons for an activation energy barrier could be "geometric". For example, a key or a puzzle piece may fit, but it has to be placed in just the right way, at just the right orientation or angle, in order to work. Pushing harder and harder will not solve this problem. Sometimes we push ourselves, things seem not to fit, but it is because we are approaching the problem at the wrong angle.
Catalysts are things that reduce the activation energy barrier. Sometimes the fence in front of the hill is too tall to climb. A catalyst is like a gate in the fence. Or it could be an environment in which things fit together more easily (e.g. it could be like having surrounding portions of the puzzle done for you, permitting you to more easily place your piece with more clues).
Behaviourally, we must be willing to invest "activation energy" into new actions and ideas. The resulting reaction may pay off, and return much more energy and meaning.
We must also search for, and be willing to use, catalysts. A social catalyst might be a friend, who could help introduce us to new friends. Or it might simply be a place where you feel comfortable -- such as a community centre, school, coffee shop, church, etc. The physical place may be a catalyst to help you meet a new friend, or attain greater social comfort.
I think therapy is a catalytic process in many ways, in that it may not always provide energy for action directly, but could help provide a "surface" in the form of a therapeutic frame, a place to re-organize our orientation to things, permitting reactions to more easily occur.