Think of something, anything. Think of it as a part of a system with modules and processes. Now, you'll notice that there are some patterns to it. Things tend to happen in some way rather than some other way. If we try to change it from the outside, the system will oppose it. In other words, the system has some momentum. This is a reason why change has to come from within. It can't be effected from the outside. A god won't save us. However, the good news is that as participants in the system, we can absolutely effect change. We just need to overpower the existing momentum.