That might seem a slightly strange question as you probably think or believe that everything you think or believe was decided to be thought or believed by you… but it that the case?
So often we roll through life under the assumption that we have taken in various info, data, opinions, facts (or things masquerading as facts) and thought it over, maybe looked into whatever it is more and then formed a picture that we think or believe is true or what it is that we decided.
How often is that the reality of what’s going on in our heads?
Take any random thing you think is what it is and reflect upon it, look into it and… you may find that someone through advertising, malicious or non malicious, intentional or not intentional steering of your views or someone telling you what it is made the decision this that was a fact and you filed it away in your head and added a tag to it that tells you YOU came up with the conclusion, not someone else.
It’s worth checking yourself from time to time, it’s worth it for all of us, all of us to do that.
You could also go down the path of looking at what “believing” something is as opposed to “thinking” something is, but at the least just doing an audit of your beliefs and what you think is reality to see if you actually decided on your own is worth while and may give you a few surprises that hopefully will lead to being a bit more careful in what you see as fact and also may serve as a reminder to stay open minded and not have everything in your mind etched in stone as new pertinent data might now be available along with your evolving and growth may offer new insight changing things anywhere from subtly to drastically.
I hope you can see how important this is.
Peace.