Holding strong beliefs about life and all that is true to life is no bad thing at all. However, there are some beliefs that should not really be tolerated because they are outright toxic and are meant to limit your ability to live accordingly.
Society is changing fast and we are witnessing a narrowing gap from what was held as generally true from the years gone by to what we have now. As such, you need to train yourself to live according to the changing circumstances of life. You have to train your ego, for instance, to lay low even in the most absolutely insane situations that are a threat to your standing.
Even in this century, there are men who really believe they cannot work under a female boss. That is a ridiculous belief and is potentially hazardous in the future. With the female gender increasingly standing up to take positions of leadership, believing you cannot be subordinate to them will actually mean that you cannot have anything to do with them in the future. That is pretty damaging especially as per the changing circumstances. Such beliefs will leave you with very little room to develop personally and realize your full potential.
Another belief is that failure is a bad thing and ought not to be associated with normal living. Well, unless you can learn how to get comfortable with failure and improve, there is no way you can be anything at all in life. Life is a struggle and you have to know what failure really is if you are to have any chance of avoiding it. It is not bad and it is only, meant to aid our cause to our ultimate goals.
Your beliefs tend to drive you. Negative beliefs will lead you to negative circumstances while positive beliefs lead you to positive situations and ultimately a positive life to be proud of.