Original

June 18, I graduated from college. Wear caps means four years of my university life is over.Look back on these four years, had a happy excitement, also have pain, pay a sweat, tears, also have the harvest and achievement. Someone said, forgetting the past means betrayal, so, we recall the past, in the future.

Corrected

On June 18th, I graduated from college.  The cap I wore meant that my four years of unversity life are over.  Looking back on these four years, I remember the happiness, excitement, and the achievement, but also the pain, sweat, and tears.  Someone said, "Forgetting the past means betrayal, so we recall the past in the future."

I wasn't sure what you meant by harvest, so I left that out.  Some of the sentences you did not put in the subject, such as when you said "look back on these four years...".

The second sentence starts out with "wear caps means", which sounds like the present tense.  Since this happened in the past you should use past tense.  That sentence also did not have a subject, so I made "cap" the subject.

The many things you mention "happy excitement, pain, pay a sweat, tears, harvest, achievement", can be listed, but they need to be parallel.  That means that they should all be the same form.

I can't say, "I like apples, grapes, pears, and eating pineapples, but I CAN say " I like apples, grapes, pears, and pineapples.  "Eating pineapples, does not fit the pattern of the others.  That is why I changed "pay a sweat" to "sweat".  

graduation

June 18, I graduated from college. Wearing caps means four years of my university life is over. Looking back on these four years, I had a happy excitement, also have had pain, pay paid a sweat, and tears, but also have the had harvest and achievement. Someone said, forgetting the past means betrayal, so, we recall the past, in the future.

Keep it up!!

graduation

On June 18th, I graduated from college. The cap I wore meant that my four years of unversity life are over. Looking back on these four years, I remember the happiness, excitement, and the achievement, but also the pain, sweat, and tears. Someone said, "Forgetting the past means betrayal." so we recall the past in the future.