I'll give you two examples, personal examples in fact, of how I listened to my own advice and won, and then didn't listen to my own advice and screwed myself over.

About a month ago, I was in a tram with some friends, when I noticed this gorgeous girl. She looked about 3-5 years my senior, great body, super cute face, blonde with glasses. I am nerdy in appearance myself; been called a pretty boy quite a few times (which isn't everyone's cup of tea), but I do tend to dress classy, often with suits and lots of jewelry. Historically, older women seemed to like me a lot, but then again the suits do give off mature vibes, so perhaps she thought I was older.

I notice her looking in my direction, but as every man does, I dismiss this as her simply looking at something else. When I noticed her staring at me the second time, with a "hmmm, interesting fellow" look on her face and a slight smile, I knew it was my time to strike. I had to ditch my friends, and since the tram wasn't crowded, I swooped in easily. I said "staring contests are not really my thing. You won this one, I admit", with a smile and got the ball rolling. A month later, we're now casually dating, or friends with benefits as kids call it.

The other instance happened a few days ago, also in a tram. This time, I did not look good whatsoever - a leg day in the gym BRUTALIZED me, to the point where I could barely walk. I was dizzy, dehydrated, and in my "incognito" outfit (clothes I wear when on some business so that nobody recognizes me). I notice this girl sitting all alone by herself, with a pissed off look on her face. When we made eye contact, a voice told me to go for it, since the seat next to her was empty. I sat down, but I didn't say anything, and I exited the tram when my stop came up. I blamed this mistake on the gym beating my behind that day, but that's an excuse. Even though she did look pissed and even though I probably would have been rejected, I still should have made conversation. "Bad day, huh? I know how you feel, trust me" - what could have been.

TLDR; if the opportunity arises, go for it. Rejection, horrible insults, a number, sex right then and there - there's literally thousands of potential outcomes, good and bad. There's nothing worse than living in regret, because the guy who gets knocked down isn't a loser, it's the guy who never even fought to begin with. Don't listen to doomers and folks of that nature - a man's ego is never meant to be stroked, it's perpetually rocked, daily, multiple times. A thousand small "no's" are insignificant compared to one big "yes."