Becoming more social out of pure frustration

I was one of those very talkative and popular guys during elementary school and high school, but then after that I for some reason developed a more and more quiet and careful type of personality some time in 2005 or so, and I didn't like that at all.
I have then remained more or less that way in front of almost everyone except my closest family members and friends, and I have noticed that this has started to make me more and more frustrated and annoyed lately.
I will think back on the school days when I always hung out with people and gave a social and spontaneous impression in front of everyone, then I compare that to how I act nowadays and I always tell myself "no, this is not me".
Of course, I also gave that quiet impression in front of my classmates at my current university, as well as basically everyone else that I run into there.

These last couple weeks this has started to irritate me more and more, even to the point that it has given me enough motivation to insist on acting in a more relaxed and talkative way in front of them.
Every time I have run into a classmate the last few weeks I have immediately reacted "no, I am not acting shy and awkward again!" - like a kind of reflex - and then I end up acting a lot more outgoing and relaxed than I usually do.
It's not so much that I have decided to start practising, it is more like an "I am so damn tired of always being awkward and giving the wrong impression, I am gonna show a more social side of myself now once and for all!" type of reaction.
And I do generally get positive reactions from this, so that's of course very motivating.

Have you ever heard of any situation similar to this?
It feels like I have finally had enough of having a personality that I don't enjoy and that this has made me aggressively start to force myself to have that personality that I feel that I should have.
It's as if I have been building up this desire for change for so long now that my patience has reached its limit and forced me to act it out.

There are oodles of Youtube videos out there about how to be more likable, etc. Haven't looked at one in ages but I think what you are doing would fall under some of what those videos would advise.

Looking back, there were many situations in which I felt socially awkward. High school dances and many party situations come to mind. In college, I would overcome the feeling by drinking too much. Some of my gfs and bfs had the abillity to make me feel relaxed but this was because we were just doing our own thing and not worrying about everyone else. Not everyone is ever going to find me interesting, funny, etc. I have mostly told myself "who cares" -- my sister was extremely popular in HS and my observation was it seemed like more trouble than it was worth. So many people put demands on her attention and time--some of them seemed like they took more than they gave (not everyone--some of her friends were great).

I do know that some people must either thrive on it or play the game because it helps them be successful in business, politics, etc. According to Youtube videos, can get more comfortable with practice. Who knows if those videos are just to attract views. Maybe they work for some. Let us know how your experiment goes......

A lot has to do with age and exposure. Both elementary school and High School provide a much smaller group of people that one can learn to navigate around over many years. This is a much more "intimate" world in that it's actually smaller as opposed to what is out there on a much bigger scale that is not so small and intimate anymore. Actually grammar school and high school is much like the safer places young fish grow up in meant to give them more safety and a better chance to grow and thrive, but as young fish grow and get bigger they have to move out to the bigger seas where they no longer that the same kind of protection they did in the safer smaller environments. Truth is that even popular kids find out that once they leave that smaller world of grammer school and high school, they are in a whole new bigger world where they have to find their way in a big sea of people than what they are used to. It's always a big adjustment because it's simply a much bigger world than what anyone is used to that finally leaves the grammar school and high school smaller world. So you are not alone in experiencing these challenging feelings you are experiencing.

Yeah, I do still sometimes meet old classmates and old friends from back when I was a teenager and I can act more reserved and careful even among some of them, but I feel more at ease with them because they at least have known me when I was my much more outgoing self, so they are aware of that side of me.
It's a lot more frustrating when I meet new people, like new classmates for example, and they never get to know that side of me and probably kinda start thinking that my careful personality is what I have mostly been like, which is not true at all.
And this false view of me has started to really annoy me hardcore lately, so that I actually get this "fighter attitude" where I make damn sure to stop acting that way.
That attitude is so powerful that it even surpasses this careful style that I have got used to throughout this last decade.

One major difference that says a lot is the fact that when I was a teenager I could easily make eye contact with girls and flirt with them without making a big deal out of it, whereas these last several years this has felt a lot more "serious" - it just hasn't had the same playful vibe to it, so I have acted a lot more serious about that as well.
But even this has started to come back to me, just because I have had this extreme desire to get it back.

It's a pretty funny situation - I am not just thinking like "well, it would be nice to practise this now", it's more like "okay that's it, I have had enough of this".

It feels almost like some sort of spiritual awakening or something;
I have even started to feel a great desire to go to parties at my university, which is funny since I have shied away from that more and more for a long time.