I have been preoccupied as of late with questions of happiness.

My friends believe that living life in the fast lane is the happiestmost blissful thing ever, because it is so glamorous.

This way is more natural.
"He said that... Blablablabla"
"I think that... Blablablabla" etc

ButHowever, being energetic sometimes makes me feel a bit uneasy, and that is the reason why my friends are always trying to convince me to get a new lease of liflive a little.

"live a little" is a common phrase we tell people when we want them to try something that they don't normally enjoy or wouldn't normally do.

They think I am so taciturntoo reserved and sullen, and that it is so obvious that if you are not vivacious enough, no girls will takebe attracted to you.

Taciturn is a really uncommon word. I would venture to say that even most native speakers don't know the meaning of it.

I once asked them if I did nowhat I should do, since I don't have a sunny disposition, what should I do?.

I just want to get away from it all and find a breathing spacsome space to breathe.

My friends believe living life in the fast lane is the happiest thing everbest way to be happy, because it is so glamorous.

You don't describe an activity as happy. You can say an activity or way of life makes you happy. e.g. You can say 'When I lived life in the fast lane, I was the happiest I've ever been'.

They really love being out and about, plartying with friends and taking part in various paractivities.

We don't usually use the word 'playing' for adults. When it is used with adults, it often is deliberately used to make the point that even adults need to play the way children do.
And we wouldn't say 'taking part in parties'. It's not grammatically wrong, just not idiomatic.

But being energetic sometimes makes me feel a bit uneasy, and that is the reason why mSuch a frantic lifestyle makes me uneasy. My friends are always trying to convince me to get a new lease ofn life.

I'm not sure what you mean by 'energetic'. It doesn't make sense that energy would make you uneasy. Maybe you mean 'frantic'? I think I might say that 'Such a frantic lifestyle makes me uneasy'.

It doesn't quite make sense that your unease would be the reason for your friends' efforts. It's your behaviour rather than your feeling that would cause friends to try to change you.

They think I am so taciturn and sullen, and it is so obvioussay that if you are not vivaciousfun-loving enough, no girls will take to you.

'Obvious' doesn't work here. And 'vivacious' is used in exactly the right way, except mostly about girls/women, not men.

I once asked them , "if I did noon't have a sunny disposition, what should I do?'

They said things likeat I needed to find my own ambitionsomething for which I had a craving, opassion. Otherwise I would become more and more pessimistic.

I just want to get away from it all and find a. I need breathing space.

Space in this case is not a countable noun, so you don't want 'a'. It's just 'breathing space'.