This one has come into play with a few guest speakers & presentations lately. It's one of those things especially to pay attention to about others. As we get older, the critics seem to come out of everywhere to knock us out of going after our dreams and goals. But maybe there is another view to take at this quote.
The other side to this is that we also have to not give ourselves permission in making ourselves feel bad. We are our own worse enemy so many times throughout our lives. That self-talk comes to mind. It's something that we need to constantly be aware of and actively working hard to deal with. If we consciously look at what is going into our heads along with catch ourselves when we start going negative on ourselves; just watch the changes that can happen in our lives. Another cool thing will happen - others will notice too. Some will embrace and cheer you on. Others will wonder what happened to you. They will say that you have changed and where is the "old" you hiding at?? When that happens.. you know you are doing a great thing. When others notice and wonder why you are different than you used to be.... that is a very good thing.
So who can you work on to not let them get inside your head? It's all about having some confidence, faith and enthusiasm for having a very positive life. This also included watching how you think too. Keep it positive. Find good things to focus on and find good things to put into your mind. Books, Audios, Podcasts, etc. Let me know what tips you have for doing this - I can use some new ideas.