Astral projection is a siddhi, a mental power of the mind/soul.

Like all such powers, pursuing them for their own sake can be a blind alley.
Meditation, without any regard to siddhis, is a better approach.
Then, mental powers may arise when we have need of them in a more natural manner.

Striving for a mental power makes the desired power elusive, like chasing a wild horse. When we are calm, the wild horse may settle down and approach us, or it may not. But with meditation we cultivate the terrain to at least bring such mental powers into the realm of possibilities.