Answer by taking a quote from the following article:

Phineas P. Gage (1823-1860) was an American railroad construction foreman remembered for his improbable[B1]:19 survival of an accident in which a large iron rod was driven completely through his head, destroying much of his brain's left frontal lobe, and for that injury's reported effects on his personality and behavior over the remaining 12 years of his life--effects sufficiently profound (for a time at least) that friends saw him as "no longer Gage". [H]:14 Long known as the "American Crowbar Case"--once termed "the case which more than all others is calculated to excite our wonder, impair the value of prognosis, and even to subvert our physiological doctrines" --Phineas Gage influenced 19th-century discussion about the mind and brain, particularly debate on cerebral localization,  [M]:ch7-9[B] and was perhaps the first case to suggest the brain's role in determining personality, and that damage to specific parts of the brain might induce specific personality changes.  [M]:1,378[M2]:C  :1347  :56

Despite his own optimism, Gage's convalescence was long, difficult, and uneven. Though recognizing his mother and uncle (summoned from Lebanon, New Hampshire, 30 miles away)[H]:12[M]:30 on the morning after the accident, on the second day he "lost control of his mind, and became decidedly delirious". By the fourth day, he was again "rational ... knows his friends", and after a week's further improvement Harlow entertained, for the first time, the thought "that it was possible for Gage to recover ... This improvement, however, was of short duration."  Beginning 12 days after the accident,[M]:53 Gage was semi-comatose, "seldom speaking unless spoken to, and then answering only in monosyllables", and on the 13th day Harlow noted, "Failing strength ... coma deepened; the globe of the left eye became more protuberant, with ["fungus"--deteriorated, infected tissue][M]:61,283 pushing out rapidly from the internal canthus [as well as] from the wounded brain, and coming out at the top of the head." By the 14th day, "The exhalations from the mouth and head [are] horribly fetid. Comatose, but will answer in monosyllables if aroused. Will not take nourishment unless strongly urged. The friends and attendants are in hourly expectancy of his death, and have his coffin and clothes in readiness."  Galvanized, Harlow "cut off the fungi which were sprouting out from the top of the brain and filling the opening, and made free application of caustic [i.e. crystalline silver nitrate][M]:54[H1]:392 to them. With a scalpel I laid open the [frontalis muscle, from the exit wound to the top of the nose][H1]:392 and immediately there were discharged eight ounces [250 ml] of ill-conditioned pus, with blood, and excessively fetid."  ("Gage was lucky to encounter Dr. Harlow when he did", wrote Barker. "Few doctors in 1848 would have had the experience with cerebral abscess with which Harlow left [Jefferson Medical College] and which probably saved Gage's life." [B]:679-80 See SS Factors favoring Gage's survival, below.)  On the 24th day, Gage "succeeded in raising himself up, and took one step to his chair". One month later, he was walking "up and down stairs, and about the house, into the piazza", and while Harlow was absent for a week Gage was "in the street every day except Sunday", his desire to return to his family in New Hampshire being "uncontrollable by his friends ... he went without an overcoat and with thin boots; got wet feet and a chill". He soon developed a fever, but by mid-November he was "feeling better in every respect ... walking about the house again". Harlow's prognosis at this point: Gage "appears to be in a way of recovering, if he can be controlled".

What was his recovery like?
Gage's convalescence was long, difficult, and uneven.