GA pilot reported a heading deviation while on the CATHEDRAL ONE Departure from PSP airport resulting in a CFTT event.

Narrative

I was departing PSP at night and decided to file IFR due to high terrain. Weather was unlimited ceiling; visibility >10 SM; light winds. I reviewed the CATH1 Departure procedure the day before and in mid afternoon before filing. I did not review the procedure again immediately before takeoff.On takeoff; I maintained heading of 310 degrees. However; at 400 feet AGL; I commenced a right turn towards PSP; instead of climbing until crossing the PSP R-268. PSP Tower transferred me to SoCal approach. Approach reported radar contact. They noted I had 'turned early; do you have terrain in sight'. Due to extreme clear desert VMC conditions; many lights and no dark spots ahead I reported 'terrain in sight'. ATC provided vectors for the climb; climb and maintain 10;000 feet which I complied with. No further action was taken. Flight continued uneventfully thereafter.Factors contributing were:1) Over confidence in pilots' memory and successful completion of departure procedure at least 2 times in previous 6 months.2) Possible light fatigue due to flight after a long work day (computer/desk job).3) Flying passenger back to ZZZ and driving to ZZZ1 for an XApm flight to the east coast. Very minor get there itis.4) Not following printed procedure card which calls for reviewing the departure procedure prior to take off.