Quenk and other researchers say that healthy use of our inferior function is the best way to relieve stress because it gives the dominant a break.
INFJ healthy use of Se--sensible exercise, cooking, playing musical instruments, detailed crafts like woodworking or jewelry making
Unhealthy use of Se--mindlessly watching TV, overeating, overexercising...
So what are the healty and unhealty use of Si?
There are some great replies here, and a lot more ideas than I had anticipated
I personally have a bad relationship with chocolate. It calms me down, unwinds and gives a wonderful sensation in the pit of my stomach. So I'm looking to replace that with something else *grin* The only thing I have that works equally well is retreating in Nature, but that is not always feasible.
I do do the surfing thing a lot as well (why do you think I'm here

), but I use that mostly to procrastinate, not to make myself feel better

Tv same thing. Crafting jewelry, I've done for as a hobby as well as professional, and I was amazed at how relaxing that can be. But for instant relaxation, it does not beat chocolate

Exercising allows me to wander with my thoughts, and then I'm back to being stressed, although dancing and singing at the top of my lungs (in some karaoke bar) is very destressing as well (but again, not always feasible, and also not handy when you're dead tired)
The rest of the suggestions, I'm going to let sink in... *smiles*