When I was a university student, I had a lot of dreams. I dreamed about having a great job which can give me a stage to show my abilities and let me practice all my creative ideas. Of course, I could earn a satisfactory salary with it. I thought that everyone can discuss things with a calm and reasonable attitude. Nobody will have ulterior motives or hurt you on purpose. 

Since becoming a senior staff member, I found that a peaceful and joyful workplace does not exist in the world. Every company has its own problems. And most employees are unhappy at work, because of their crafty, weird and stupid bosses, the dull job assignments, unfair salaries, and the office politics or conflicts.

Every year, lots of unhappy employees would like to have a new job and thought this would give them a whole new life. Unfortunately, sometimes they will find a cruel reality which is the job you would like to have might not be as good as you thought. (The job itself is just as the encircles person in the town wants to go out) I didn't understand this part of your example, the person outside the city wants to come in.

Well, I don't mean to complain about my job, I am just realized the gap between dream and reality. Nonetheless, I have to cheer up, be myself, keep calm and fight with the realities, while never losing too much purity and kindness in my mind.

The Gap Between Dreams And Reality

When I was a university student, I had many (a lot of) dreams. I dreamed/dreamt of having (to have) a great job which could (can) give me / provide me with ...a stage to ... show off / display (contribute) my abilities / talents (,) and also allow me to  / let me .... practice/practise  all my creative ideas. Of course, I could earn a comfortable salary at the same time. (satisfied salaries through it.) I thought that everyone would (can) discuss issues (things with) in a calm and reasonable manner. (attitude.) Nobody would (will) have ulterior motives or hurt you on (in) purpose.

Once (Along with) I became (become) a senior member of staff, I found that peaceful and joyful workplace, once longed for, does not exist. (is not exist in the world.) Every company has it's own problems. More so, (And) most employees are unhappy at work, because of the unscrupulous behaviour of their (crafty, weird and stupid) bosses, the dull job assignments, unfair salaries, and the office politics or conflicts.

Every year, many (lots of) unhappy employees consider changing to (would like to change) a new job, thinking it (and thought this) would bring (give) them a whole new life style. It is unfortunate but (Unfortunately, sometimes) they will sometimes be faced with the harsh (find a cruel) reality that (which is) the job they covet (you would like to gain) might not as good as they imagined it to be. (you thought.) The grass always seems to be greener on the other side, (job itself is) just as the (encircles) city dweller longs (person in the town wants) to leave (go out), whilst others dream of working and living in the city. (the person outside the city wants to come in.) 

Well, I don't mean to complain about my job, I (am) just wanted to emphasise (realized) the gap between one's dream and the reality. Nonetheless, I have to cheer up, be myself, keep calm and be realistic (fight with the realities.) but, at the same time, resolve to never lose my (change too much) purity and kindness of (in my) mind.

Very good account of the realities of working life v the perceptions beforehand. I have offered a few other phrases we may more commonly use to help the read. In the third paragraph you seemed to change tense half way through, referring to 'them' and 'they' before changing to 'you' so I have corrected that. Well done!