It´s no good pushing something that is simply not there.

My try:

Sýrf yok olmadýðý bir þeyi sürdürmesi iyi deðil

How about

Olmayacak bir þeyi zorlamanýn anlamý yok.

which word is sürdürmek? is it "to push"?

and does this sentence talk about that someone keeps doing something?

Honestly I don´t understand the English sentence, but what you wrote in Turkish is not logical although it is pretty nice as grammar.

sürdürmek is keep doing something

you wrote olmadýðý bir þeyi sürdürmek, it sounds like "he keeps being something which he is not" but you put one "yok" before it, and that makes everything confusing

´Pushing´ meaning ´forcing´ (someone to do something they do not want to do or feel like doing)

Thank you guys!!

Being corrected is the best way to learn.  Btw: what´s the opposite of ´var olmak / exist´??

The only thing i could think of was ´yok olmamak´, but that´s obviously totally wrong.

And the pushing-thing: i understood it as ´continuing´-ish.  (as in f.i. continuing a relation although love has long since gone)

yok olmamak is the negative of the opposite

yok olmak is the opposite of var olmak

we use "yok olmak" for "to be terminated" as well