...Such a Depressing Entry (reader discretion recommended) :]

...Such a Depressing Entry (reader discretion advised) :] (On TV shows, there is a standard warning that says "Viewer discretion advised". I've never read anything like that for a text :D but I guess I'd use the same phrase.)

I'm in California, US, on a "family" trip at the moment. (Good sentence)

This trip has been very helpful and even refreshing to me so far in that it has revealed the unmistakable/unequivocal and irreversible incompatibility between me and my family. ("it's" is also grammatical, but in this specific case I feel that "it's" would probably mean "it is". Yeah, don't know why I feel that way, sorry! :D. How was the incompatibility "decisive"? I've suggested some different words that are closer to what I think you meant to express. If there is incompatibility among your entire family, then your mother might also be incompatible with your grandmother, or your sister with your mother, etc. Since I think you only meant to say that you are incompatible with the other members of your family, I've changed it to mean that.)

Last night, frustration and (a sense of) despair swept over me. (Why water it down? Just go with a full-on wave of despair! :D)

I could only resort to sobbing to myself in my bed for a good one hour or so.

It surely had a bit of a cathartic effect on me, leaving me with an expected splitting headache and miserably swollen eyes. (Catharsis is a profound thing. I wouldn't try to express a little bit of catharsis. If you think catharsis is too strong a term, you could go for a lighter word, such as 'relief'.)

About thirty minutes or so ago they burst into blaming me for incessantly being ill-tempered and screwing up their trip. ("Burst into blaming" is some peculiar phrasing, but I'll allow it. Good sentence)

I'm just not capable of doing anything about it. (Good sentence)

What are you supposed to do when you find your own family the most despicable, obnoxious creatures on this planet? (Is the extent of their obnoxiousness despicable? If so, your version was correct. I've gone ahead and interpreted it this way, though. ^^)

How can I stop feeling like destroying myself? (Good sentence)

I wish I had two lives or more so I could experience killing myself and still have a second chance. (Good sentence)

Not that I'm desperately wanting to die or anything, but I envy a girl we had back in my high school, who created hydrogen sulfide in her bathroom and killed herself. (Good sentence)

My life could end just like that too. (You are describing a general truth, right? You are stating the possibility that your life ends in this way. If this interpretation is correct, then the present tense is required. In your version, it sounds as if there was a time where this was a possibility, but it's not anymore.)

I'm everybody's pain in the ass. (Good sentence)

Apparently I don't even have the right to feel whatever I want to feel. (Good sentence)

*DISCLAIMER* (Good sentence)

This is just another one of me being (or: this is just (a blog written during) one of those times where I feel) desperately emotional and stuff.

Never take this seriously. (Good sentence)

Thank you.(Good sentence)

Now ignore the content and help (me) improve my English, please >_<; (Good sentence)