Pisces male coworker upset at me

hi all, i've been a long time lurker but this is my first post. i recently had a small 'feud' with my pisces (male) coworker. a little bit of a background, we have been working together for couple years and always have good relationship, which unfortunately sometimes involve me bending over backwards to help him (i do like to help people out so i really don't mind helping him). however, few days ago, he was asking my help to do something which i thought was unnecessary because management did not request it. i told him i could help him with it, but i had to leave shortly due to other appointments. that's when he flipped and got very upset, saying that he was disappointed and and basically just shut me out. our relationship was very good before, so this came as shocking to me as i thought i would be able to reason with him and he would at least listen to what i had to say (which he always did before).

since then he has been acting very cold towards me and refuses to talk to me. do pisces men usually hold onto their anger for long? i am just confused because to me this does not seem like a big deal (it's not like i left him alone in the middle of important project/deadlines). or could it be that this is a big deal to him but i just didn't see it? should i apologize to him? we do work very closely together and i like working with him so i really don't this to ruin our working relationship. on a side note, he was having a rough week so i was also wondering if he just lashed out and took it all out on me.

more info with his sign: he's a pisces sun with taurus moon. i am a leo woman with gemini moon. thanks guys, any inputs will be helpful.