For our purposes here, since not everyone reading this is a man and not everyone is married, feel free to substitute woman, and/or partner, and/or friend.
I looked up the word sympathetic in the dictionary. While the first definition was somewhat benign, what struck me more was the list of synonyms:
Compassionate, caring, concerned, understanding, comforting, sensitive, understanding, encouraging, considerate, kind, tenderhearted, pleasant, agreeable, friendly.
With someone like that at your back, there is nothing in the world you couldn't do, be, or achieve. It'd be like your own personal cheerleading squad. Go! Fight! Win! Our world could really benefit from more spouses and partners like this. Unfortunately, too many individuals and families are on the receiving end of the opposite.
I was also intrigued by one of the secondary definitions for sympathetic: showing approval of or favor toward an idea or action.
To me, that implies a degree of trust and possibly risk tolerance. If we show favor towards action, what we are in effect saying is, "I trust you. I believe in you. I don't know how this will turn out, but I will support it anyway."
To have a person like that in your corner would be a treasure of infinite worth. And if you are fortunate enough to have someone in your life like that, let them know how much you appreciate them. Often.
To your good fortune!