Feeling mad for no reason

Let me start this off by saying I’m very happy in my relationship. My girlfriend and I both need space away from each other so some days we don’t talk. Yesterday was a rough day for me mental health wise and I didn’t feel like talking to anyone, I just sat home and tried to distract myself. Then when I’m laying in bed trying to sleep I suddenly get upset that we haven’t talked all day and this morning I woke up mad at her??? I have no reason to be angry but I am and I know the solution is to just talk to her but I can’t until late tonight so I’m just venting my feelings