Cissy's notebook entry: Apr 25, 2010

I feel down these days. Despite the translation task and those tiresome experiments. The relationship between one and another made me out to max.. I am not able to be smily sometime, tears run out and  no will keeps them back. After this period busy with the mice and homework, I want to take a journey to cheer myself up.

This should do a little help to you.

Cissy's notebook entry: Apr 25, 2010

I feel down these days. Despite the translation task and the tiresome experiments, the relationship between one and another made me maxed out. I am not able to keep smily sometime, tears run out and I have no will to keep them back. After this period busy with the mice and homework I want to take a journey to cheer myself up.

In short there's no big errors in your writings. I've made a few adjustments though, I think this looks a bit better:

Cissy's notebook entry: Apr 25, 2010

I feel down these days. Despite the translation task and the tiresome experiments, the relationship between one and another got me burned out. I am not able to keep happy sometimes (or: I'm not able to keep smiling sometimes), tears run down (or: come out) and I have no will to keep them back (this sounds quite poetic actually =]). After this busy period with the mice and homework I want to go on a journey to cheer myself up.

Hmm, I'm not sure about the preposition 'despite,' internet tells me that it should be 'despite' or 'inspite of.' 

Cissy's notebook entry: Apr 25, 2010

I think you have to use "Despite" with preposition  "of" . For examle Despite of something.