I'm sure this is a touchy subject for many. I still experience both sides of it and constantly check myself when I realize my words and actions err on the unsupportive or judgmental side. Is it a fear of being left behind? A concern that the person making improvements won't share common ground when they reach their ambitious goal? The audacity! Humans are so fearful, often for no reason.
When I didn't drink for 30 days last fall, certain friends distanced themselves from me. When I announced that I'm going to pay off my student loan debt before my 30th birthday, I was met with skepticism and, "Yeah, right!" even from some of my closest friends. Some even rolled their eyes! I'm not sensitive enough to think they meant to hurt my feelings, but the you-can-do-this comments were few and far between in real life. When meat eating strangers find out I'm vegetarian, some meet the news with a, "So, you think you're better than me?" sentiment, incredulous. So what gives? I still don't understand it completely but I think recognizing it for what it is equips me with the sass to keep moving forward, always. And in the words of the great Johnny Depp, "Just keep moving forward and don't give a shit about what anybody thinks."
Observe and acknowledge the loved ones that never doubt you and thank them for it. If they aren't your cheerleader right away, don't dwell on it. Move on. For me at least, the people who matter the most have always come around.
