Rather meaningless tautology.

What it should say is ''We are all prisoners of our own negativity'' - the use of captivities is not only ungrammatical, it is also unneccessary.

The meaning is then a bit clearer which is to say if we are negative in our attitude we limit ourselves, (regardless of reality).

For me this meas that if a person has negativity towards a certain thing or person, he/she would never try to approach that person or thing against whom he/she harbors negativity, hence limiting themselves to newer experiences.