Is it G or H?
You could memorize instead something like
P is proportional to exp(-H/RT) because it resembles a distribution hence costs no additional memory effort.
Consistency of the units should tell you where there is a ratio of pressures, or possibly where a pressure reference is implicit (a bad practice leading to errors). You take the Log(), sin(), exp() of numbers without dimension (which includes angles), not of a pressure or a temperature. So E/RT is a good candidate in an exp() while P alone is a bad one in a Log(), suggesting an implicit P0 or a P2/P1.
Alas, implicit references are frequent in thermodynamics, and when a Log is involved (notably in the entropy) it can become an additive constant, more difficult to track. Sometimes the bad habit is generalized, like the noise power density as dB/sqrt(Hz) in electrical engineering, a unit that makes formally no sense.