Old starwars:
"The force" is similar to: Chi / Prana / Mana / Life-force, but has its own weird interpretation.
The "balance in the force" comes from the idea of balance between Yin and Yang.
The "force-push" is similar to certain martial arts techniques.
The "mind-manipulation" is similar to hypnosis variants.
The "force-lightning" is more related to myths.

It is easy to learn to sense it, but...
You chi can be low due to a lot of thinking or sitting. And then it is much harder to sense it.

With deaths or sacrifices, sensitive people can feel changes in the life-energy. Certain traditions used this to collect a lot of life-energy. They hoped to manipulate matter with it, but often these cause hypnosis instead. Like a war-trance that soldiers can get.

The concept of life-energy was forbidden by the church in the middle-ages, due to its relationship with previous cultures. Later scientists forbade that idea due their belief in materialism/scientism. Still there are many scientists working on it, each with their own theories.