Note: I’ve since stopped using Journal Cards out of an aesthetic preference for more conventional journaling, but the many benefits of journal cards are still worth considering.
Using index cards for a daily journal yields a number of benefits beyond the expected cost and portability. In keeping a small stack of cards in your Every Day Carry (EDC) it becomes trivially easy to journal anywhere, anytime. The modularity of cards also allows me to insert or rearrange entries, say if I forgot a day earlier in the week and wanted to journal retroactively. This method also allows me to journal discretely on the go without risk of ruining, losing, or otherwise exposing my journal in an undesired way. All other entries remain safe and private at home.