What kind of trails? Are you talking about smooth paved trails or rocky mountain bike trails? If you are talking about rocky mountain bike trails, is your bike rigid or suspended?

If you are on smooth trails like bike paths or even smooth gravel paths, lower pressure causes more deformation of the tires which results in more energy loss through the constant flexing of the tire. That creates friction which is energy lost where you don’t need it. There is a balance, however. If the pressure is too high, the tires will bounce on impacts so that your energy goes into lifting the bike rather then propelling forward. I would say that the balance is much higher than 38 psi on your width tires at your weight on a solid surface. Tires on roads and paved trail should be firm enough to not squish down too much but not hard enough to bounce off road imperfections. If you can feel your tires bounce with each pedal stroke, they are too soft. With the proviso of smooth (or smoothish) surface trails, I’d run pressure at 20 to 50 psi higher. The bike will roll faster.

If you are talking about rocky trails, I’d increase the width of the tire to at least 55mm (2.1”). The pressure you are using now would be good for that wide a tire. Much lower for your weight increase the chances of the rim impacting the ground on big hits. That can lead to rim damage which is an expensive repair. The lower pressure will probably make you slower but rocky trails are usually thrilling enough that the slower speed makes little difference.

I’d also add suspension if you don’t have it now. Controlled suspension...not just springs or bumpers...keeps the bounce from impacts from controlling the bike. You can keep a straighter line because when the tire hits something and wants to bounce off-line, the shock absorbs the bounce and allows the bike to keep running in a straight line. Suspending your body above the bike also helps. Your legs and arms absorb shocks as well.