Emotional barriers to something completely within reach

So, because this issue is particularly personal, I am going to leave it vague. Also, I think most people, especially volunteers, experience this with something, whatever it may be.

There is something I'm not doing here that I am supposed to do, and want to do. It's pretty fundamental and essential for the work I need to do, the work I want to do. But, still, I don't do it. Logically, it's within my reach. I KNOW I can do it, but emotionally I FEEL that I can't - that the glass on the table is completely out of reach. So, when people walk into the room and ask why I'm so thirsty I make a joke about the glass, say I don't want what's in it, give any excuse for not just reaching out, taking the glass and downing it. I can light candles, I can make a four course meal, I can play obscure music and change the temperature. But I cannot drink from that glass. When people leave they remember the food, the setting, their own drink - the glass is only a funny reference, with the jokes even supplied by me. But when they leave, it's just it and me. And a mouth dying of thirst.