Moments of success in life

Probably not incorrect, but 

Sometimes, success seems rarely to be possible in life. just seems more natural.

[But there are moments when you work very hard to achieve a certain thing in your life] that [you will experience indeed success].

"that" is not the right joiner for this, a it is, I suspect.

[But there are moments when you work so hard to achieve a certain thing in your life] that [you will experience indeed success].

So, for example I thought I will would never show improvement in my English class test but I was wrong.

I have got 2 days before ago, my last English exam back from my teacher and I was so suprised when I saw my mark. So never give up about on things and always continue to work hard even if it's seems impossible. :-)

will --> would (conditional)

(never) give up on things

.. it is impossible = .. it's impossible

or

.. it seems impossible