For each skill check the player rolls 1D100
If the player rolls higher than the current skill number, or the result is over 95, then the investigator improves in that skill: roll 1D10 and immediately add the result to the current skill points. Skills may rise above 100% by this method.

If the player rolls equal to or less than the investigator’s skill level, then the investigator hasn’t learned from the experience and the skill amount does not change.
Page 95

an investigator may choose to spend time with one entry listed in their backstory which could act as a form of psychological support; clearly this does not include phobias, manias, wounds or anything to do with the Cthulhu Mythos. This may be done during downtime between adventures or during the investigator development phase.

The player should go into some detail about what their investigator is doing to seek healing or redemption. The actions should be thematically appropriate to their backstory; perhaps the investigator is going on a religious retreat or a holiday with a loved one

The player then makes a Sanity roll. Keeper and players are encouraged to roleplay the scene to the point where it comes to a head, and then make the Sanity roll, roleplaying the outcome. If the roll is successful, the investigator gains 1D6 Sanity points. If it is unsuccessful, 1 Sanity point is lost, and the Keeper and player should revise that aspect of the investigator’s backstory in some way to reflect the failure. Thus the religious retreat might result in a complete loss of religious faith, or a family holiday might result in separation or divorce.

Each investigator begins the game with one backstory entry that is especially important to them: this is their “key connection”. If the player chooses to use their investigator’s key connection, they are granted a bonus die when making their Sanity roll. In addition to the 1D6 Sanity points gained for a successful Sanity roll, the investigator will recover from any indefinite insanity. If the Sanity roll is failed, that aspect of the investigator’s backstory is revised, and that investigator no longer has a key connection.

In time, the investigator may form a new key connection. During a future investigator development phase, a backstory aspect may be converted into a new key connection if the player successfully uses the “self-help” option to regain Sanity points via that connection. Alternatively, any Sanity roll of 01 (critical success) allows for the immediate nomination of a new key connection to replace the one that was lost.

Note: Current Sanity points can never increase above an investigator’s maximum Sanity (99–Cthulhu Mythos skill)

Psychotherapy: intensive psychoanalysis can return Sanity points to an investigator patient. Make a 1D100 roll against the analyst or doctor’s Psychoanalysis skill once per month.

If the roll succeeds, the patient gains 1D3 Sanity points. If the roll fails, add no points. If the roll is fumbled then the patient loses 1D6 Sanity points, and treatment by that analyst concludes—there has been some sort of serious incident or dramatic setback in the therapy, and the relationship between patient and therapist has broken down beyond saving.

Therapy can also be used to remove a phobia or mania. At the end of a month the analyst rolls for success in the same manner as detailed above. If successful, the investigator then makes a Sanity roll. If both rolls are successful the phobia or mania is cured and erased from the investigator’s backstory. This benefit replaces the Sanity point gain and no such points are awarded. Failure of either of the rolls bestows no benefit. Fumbling either of the rolls results in a loss of 1D6 Sanity points (as above).

A player should keep track of the Sanity points lost to any given Mythos entity. With every investigator development phase (see page 94), the player should reduce all those numbers by 1—time is a great healer.