Student pilot reported lack of urgency to descend for conflicting traffic resulted in a NMAC.

Narrative

I was flying a true course of about 131 degrees; when NORCAL TRACON called an aircraft advising them of traffic. NORCAL received no response. NORCAL then contacted me; advising me of traffic in front of me at 3800 [ft.] MSL. This leads me to believe that the aircraft that did not respond was the traffic that ZZZ was now advising me of. NORCAL 's call to the unknown aircraft and their call to me were within seconds. After sighting the traffic; I told NORCAL I would descend to 3300 [ft.] MSL until the traffic passed. ZZZ acknowledged. I did not descend with urgency and only reached about 3400 [ft.] MSL before the traffic passed. Without NORCAL; I might not have seen the traffic.One human performance consideration is the over reliance on TRACON and other controllers to protect the pilot. The pilot must be responsible for themselves. Complacency is also a danger to pilots. After seeing the traffic; I did not feel urgency to get 500 ft. clearance. I also had more stable cruise than my last training flight; and I did not want to ruin it with an urgent descent; so I only descended mildly.