Hakeem ul Umma Mawlana Ashraf Ali Thanawi (Allah have mercy on him) tells an anecdote in one of his discourses:

A sufi aspirant busy with his islah (reformation) was overwhelmed with a thought of abandoning his spiritual struggle and to enlist in the Muslim Army engaged in Jihad. Being sincere he consulted his Shaykh before embarking on this holy journey.

Sheikh admonished him saying that this was the conspiracy of his nafs (lower self) to escape.

The nafs was tired of the daily jihad (struggle). That is, struggle of withholding it self from all the haram (forbidden) activities and engaging in extra (nafil) worship. For example, avoiding lustful glances, backbiting, anger, self-pride etc. and being humble, patient, pious, etc.. Tired of this daily struggle it wanted to escape by dying fighting in Jihad.

This might be the reason of calling the daily struggle of self-reformation (islah) Jihad e Akbar (The greater struggle) as compared to the holy war, Jihad e Asghar (The lesser struggle) in one of the Prophetic narrations (dha’eef).

At this point it is most appropriate to clear any misconception about Jihad in our days.
Sayyidi wa sanadi Mawlana Mohammad Taqi Usmani sahib (Allah preserve him) explains:

“Jihad is, no doubt one of the intuitions enshrined by Islam. But it does not mean a war to compel people to accept Islam, as the Holy Quran has declared that there is no compulsion in religion. Nor does it mean to occupy lands and extend territory of a Muslim state without a just cause.

Jihad is in fact means a well disciplined struggle against aggression and oppression. The struggle of jihad may be with or without arms. Armed struggle is allowed only when peaceful means have totally failed.

Apart from a just and rightful cause it is necessary that it is carried out under a competent Amir or leader in strict compliance with dictates of Shariah.

This armed struggle can never target innocent persons.
It is always a legitimate struggle against an oppressor or a tyrant and his warriors.

It has, therefore, nothing to do with terrorist activities which target innocent people and have been termed by the Quran as ‘Fasad fil-ard’ (spreading disorder in the land).”

Source:Usmani M T, Albalagh International: Vol 16 No. 8/September 2005 “Islamic vision on interfaith cooperation for peace”