Noted gym scholar Ronnie Coleman said it best: Everybody wanna be a bodybuilder, but nobody wanna lift no heavy-ass weight.
Getting a pump and feeling the burn are easy, but getting stronger year in and year out is hard work. Setting PR's requires focus, determination, and consistency.
For this reason, reserve most of your mental energy for getting stronger. After you've warmed up and have begun your training session, start off with your heavy compound movements and try to set PR's. Rest fully in between sets and psyche yourself up appropriately.
After the heavy work is done, it's time to have some fun. Choose some targeted movements and seek the pump and burn. Don't work yourself up too much mentally, just bust out some medium to high rep sets with short rest periods. Don't be overly concerned with setting PR's during pump work. Focus on feeling the targeted muscle taking on the brunt of the work and fully fatiguing the fibers.
The majority of your mental energy should be focused on gaining strength through the big basics such as squats, deadlifts, hip thrusts, bench press, and chin-ups. However, some of your mental energy should be focused on muscle activation and inducing metabolic stress.
Becoming freakishly strong at the big basics through a variety of rep ranges might be the source of 80% of your hypertrophy gains over time, but if strength alone is your sole endeavor, you'll likely leave 20% of room on the table for maximum muscularity. The increased satellite fusion, hypoxia, occlusion, and cell swelling that accompanies pump and burn type training provide the icing on the cake, and this adds up over time.
Sticking to solely heavy work or solely high-rep work won't build the optimal physique. You need the best of both styles of training if you want to reach your maximum muscular potential.