Let's generalize for a moment here (actually what follows is not a generalization but my personal experience which I pretend to be general)
...when you talk to the woman or the girl you're with, the so called partner, and express whatever feeling of discouragement or desperation or weakness, she will immediately give you words of continuous and pressing solidarity that will revolve around the concept that whatever feeling you are experiencing it is simply not true. It is unmotivated. It is silly. It is probably the opposite, instead. There probably is some detail you didn't considered thanks to which things aren't so bad. You are probably doing perfectly fine. It goes so much so that you both get to a stage where she asks: "what's going on?" and you quickly: "nothing!" although you really need to talk. Because her prompt caring denial would be worse than silence.
On the other hand if you talk to your ex or to a girl you're friend with, you have a chance that she might express her solidarity in a less censoring way, which --if talking serves a purpose-- is the only way for you to move forward. She might even find the words to look in dismay at your condition without denying it. That's because she doesn't feel threatened by it. You're not her man, so your defects can be observed more objectively. This might explain why men seek love and then get bored by it. And why they keep falling in love with friends and exes. And why probably your girlfriend is a splendid talker and listener and helper --but not with you.