Everyone is entitled to their opinions, and in fact, I am not sure it would be possible to stop some people from having them. Lots of them. But there’s a difference between having an opinion and expressing it, and also a difference between having an opinion and believing that somehow your opinion is the only right one to have. Or, worse yet, believing that your opinion entitles you to trying to coerce others into agreeing with you.
For example, let’s say your friend has set her sights on a particular career and is working hard to achieve that goal. If you have concerns about that career (safety, legality, suitability), then you are entitled to express your concerns once or perhaps twice. But only as concerns, and only as your opinion. Beyond that, as long as the career is not self-destructive, it is none of your business what your friend is planning to be, and in fact friendship demands that you be supportive of her choices.
But what if you think it is self-destructive of your friend to pursue her chosen career? First, ask yourself if you are truly seeing things from her perspective, or whether you are instead judging her choices by your own preferences. What you may think is self-destructive may not have any reflection in reality if you aren’t separating your own preferences from your friend’s.
For example, perhaps you have a friend who is really well suited for the corporate lifestyle, but you personally would find that lifestyle stultifying. Don’t tell your friend to abandon her plans if that is your only concern.
Let’s put this another way. You hate chocolate ice cream, and your friend loves it. But because you hate it, you tell your friend not to eat it either. You may even threaten her by saying such things as, “I will never talk with you again if you eat that flavor of ice cream.” At that point, your friend would be perfectly entitled to reconsider her friendship with you, because friends don’t try to control their friend’s lives.
What if it turns out that the career just doesn’t suit your friend, or she loves it for a while, but decides eventually that she wants something different? Fine. It is her decision, not yours.
Ultimately, if you find that you are often telling your friends and family what they should and shouldn’t do with their lives, or, worse yet, find that you are threatening them if they don’t do what you think they should do, then that is your problem, one that you need to deal with. You don’t have the right to tell others what they can or can’t do with their lives. Sometimes it is neither prudent, politic, nor polite to state your opinion. This is called holding your tongue. It can also be called keeping the peace.