First post, so proceed with caution but I've been lurking for a while (background below).

Keep on smiling.

Today I was at the gym and there was this really cute girl that I wanted to talk to, but she was on the treadmill. I figured, if by chance, after I got out of the locker room and she happened to be walking to the women's locker room, I would strike up a conversation. I'm a confident guy, and I was self-talking to get pumped up, even though it likely wouldn't happen.

Lo and behold, she was off the treadmill - fate, right? But tragedy struck. I saw her at the water fountain ready to head towards the locker room when she had the most exhausted, fed up "don't talk to me" look on her face. It intimidated the shit out of me. I smiled at her and she didn't change expression at all. She was either not in the mood or very exhausted from her workout.

Dejected and pissed at myself, I tried to find a positive out of that interaction. And then it hit me: I do the exact same thing at the gym...and actually most of the time I'm walking. When I'm at the gym, I get down to business - and it's not pretty. I usually look pretty pissed to psyche myself up. And I don't have a very warm expression on my face when I'm relaxed. After being on the other side of that, I can now see why girls aren't giving signals that suggest "oh you're cute, I hope you talk to me." If you don't smile, and you aren't inviting, you'll never get the subtle hints from women that they are interested. This girl was far from smiling, and all it could make me do was freeze up and not want to talk to her.

So please smile - for your sake. I'm making an effort, starting today, to be happier in my natural state, and you should too. I don't want to see a woman scowl at me, and they don't want to see it either. But now that I know this, if I see that girl at the gym again, I'm not screwing up twice.

TL;DR: Maybe the reason women aren't hinting their interest is because you're projecting cold body language. Be happy, it will make you more inviting and receptive to flirting.

(Background: I just got out of a 1.5 yr relationship with a woman I thought I was going to marry. It's been a tough 4 months since, trying to pick up the pieces, so I've been lurking on here trying to regain my confidence and see how I can possibly manage to kill this one-itis - I've never dated a woman this beautiful (she was a model) or intelligent before, so the hardest part is thinking I'll find another woman of equal or greater caliber. If you're in Boston and need a wing I'd really like to get out there.)

EDIT: This article was perfectly timed - eye contact and a smile from a woman are better than scowls. For the record, my friend is the "Professional Wingman."