<human>: We've been together for 3 years and this has become a noticeable problem only recently.

During the day, I'm at work while he's in school. While we're apart, I sometimes tend to imagine things we could do afterwards, so we don't have to sit home. Whenever I think about our options, I never take in account that he might be tired or have different things to do. That always leads to me getting very upset if he says we can't do whatever it is I wanted. Actually 'upset' isn't the right word. I feel almost physical pain in my heart, like tightness and like I could start crying if just one more little thing goes wrong. Then I become more distant and it drives my SO mad, and then I get frustrated, because I feel I can't control my reaction and don't know why is that always happening, and how am I supposed to explain myself to him, and why can't he understand and yadda yadda yadda... Just bunch of confusing thoughts at the same time and the rest of the day is ruined.

My question is what in the world is my problem? Why would I take my 'plans' so seriously and why can't I accept the reality of whatever happens in a normal way?

Can you summarize the given text in a few sentences?
<bot>: I've lately been getting very emotional when my plans get rejected by my SO. Don't know why; am here to find out.