Let go of the Past

Letting go of the past and old beliefs is very important in order to learn something new - to grow and improve further.
Just as when a bird wants to fly, he has to let go of the branch he is sitting on and holding to.

Similarly, to achieve the highest potential of our life, we must let go of the branches we are holding.
The branches we hold onto are the mental, emotional, and physical attachments.

We hold on to certain beliefs, concepts, and dogmas in our minds and emotionally get attached to them - which, eventually, bind and restrict us and do not allow us to see beyond those beliefs.

Then there are physical attachments.

We hold on to some branches for security and assurance - such as certain people, possessions, and positions we have or want to achieve.
As long as we are attached to any or all of the above branches, we will always be afraid of letting them go or losing them. 

We will always want to hold on to them firmly to feel safe and secure.

However, if a bird does not let go of the branch it is holding, it will never be able to fly.

Similarly, if we do not let go of the branches we are holding, we will never be free and will never be able to rise above our current state of mind.