For longer prose like this, it might be better to post it in the notebook section. The notebook gives us more tools to work with such as highlighters and coloured text :). I will still try to edit the sentences, though I cannot assure that they are translated correctly.
那一天我漫步在夕阳下 .
I walking under the setting sun that day.
看见一对恋人相互依偎
I watched lovers embrace each other
那一刻往事涌上心头
a memory appeared in my heart at that moment
刹那间我泪如雨下
this time my tears fell like the rain
昨夜我静呆立雨中
I was standing in the rain last night
望着街对面一动不动
I kept myself from looking across the street
那一刻仿佛回到从前
at that moment a similar feeling returned
不由得我已泪留满面
so I could not stop shedding tears
至少有十年不曾流泪
it has been at least 10 years since I have cried
至少有十首歌给我安慰
there are at least ten songs that give me comfort
可现在我会莫名的哭泣
but nowadays i always cry without any reason
当我想你的时候
when i miss you all the time (not sure how to change this one, possibly "Because" instead of "when")
Hope this helps a little and that I have maintained the meaning of the poem.