In sports, a team that has the momentum is on the move and is going to take some effort to stop. A team that has a lot of momentum is really on the move and is going to be even harder to stop.
In physics, momentum refers to the quantity of motion that an object has. A sports team that is on the move has momentum. If an object is in motion i.e. on the move, , then it has momentum. So a small heavy marble moving at the same speed as a large light ball has more momentum, and you will sure feel this difference if they hit you. This is because the amount of momentum that an object has is dependent upon two variables: how much stuff is moving and how fast the stuff is moving.
In life, momentum is generated from the intentional energy you put behind your vision and the number of acts you dedicate to that vision. Acts can also be defined as action, which is energetic activity, habitual or usual acts, conduct, behaviour or, simply, something done or performed.
If your intentional energy is low or weak, it affects your life momentum. If the number of acts is few or inconsistent, it reduces your momentum. So if you are stuck, start by looking at these two dimensions.
Intentional energy can be assessed by the resources you allocate to your vision. If you are constantly postponing something because you do not have the time, then you are manifesting weak intentional energy. By consciously increasing the time you allocate to your vision you increase this dimension of your life momentum.
If you increase the acts that you perform towards your vision you also increase your life momentum. You could set yourself the goal of doing something everyday towards your expected outcome.
And if you do both you give yourself and even greater chance of getting to your vision. I know people who stay on one axis, and making no progress, begin to give up on their vision, and so feel stuck.
If you are feeling like that, look at your intentional energy - how much you want to achieve your vision, and how much you are putting into it, as well as your actions - what you are doing, and how often, to achieve it.