I really do not care what other people think, with a few exceptions.
Just like an anus, everyone has an opinion. Just as you need to really make sure that someone really and truly needs to see your anus before you show it to them, likewise - you need to really make sure that someone needs your opinion and would be receptive to it, prior to giving it. Most of the people who offer their opinion fail to understand this.
In psychological terms this is called the anus/opinion paradox.
So, if someone likes or dislikes what I choose to do, I truly do not care - because - for the most if I wanted someone to comment on my course of action, I would ask them. And because I did not, it should suggest that I value their opinion as much as I would value an offer for them to show me their anus.
See how this works?
Think of it this way: If someone thinks you should slow down (and they are so self centered that they think they should tell you - as if their opinion mattered), you could very easily counter their opinion with an equally valid (to you) opinion that, "no, you should speed up".
Is that an issue that warrants one party showing the other his anus?
No. But to avoid confrontation seems childish, so maybe a befuddled look while stating "Why would you even say something like that?" This would make them realize that you do not value their opinion more highly than you value your own opinion. Then you could say "You know, there is this guy on this forum I read and he recently said something about this anus/opinion paradox thing, and because I am sure you are familiar with it, there really isn't any need for us to discuss it further, but thank you just the same".
The exceptions: If someone is about to make a truly tragic decision (most of which are immoral - say, like cheating on his wife), or if someone is about to do something that could cause them harm (like tearing down a load bearing wall or driving drunk) then we are obligated to tell them the truth (as softly as possible without sugar coating it), even if that ruins the relationship. The only other exception - I do care, very much, if I have offended someone by saying or doing something offensive, intentionally of otherwise. Then I care deeply and do everything possible to make restitution. That is another good reason to reserve offering your opinion to those few times that it really matters.
Now be forewarned: Everything is different if this is a relationship with women. I caution you that if a female with whom you are in a relationship endeavors to give you her opinion, it is NOT GOOD to say "can't you just show me your anus instead?".
Trust me on this.