We have many friends in our lives, but there is only so much a friend can help you. No matter how close they are, how much they love you.. They cannot help you when you ultimately need help. Guru Ji explains this in Sukhmani Sahib..

ਜਹ ਮਾਤ ਪਿਤਾ ਸੁਤ ਮੀਤ ਨ ਭਾਈ ॥
Where there is no mother, father, children, friends or siblings

ਮਨ ਊਹਾ ਨਾਮੁ ਤੇਰੈ ਸੰਗਿ ਸਹਾਈ ॥
O my mind, there, only the Naam, the Name of the Lord, shall be with you as your help and support.

This particular place can be thought as the process we all go through after death, where we have to face the punishments of the Jamdoots and have our lives analysed by Dharamraj. This is made clear in the next pangti..

ਜਹ ਮਹਾ ਭਇਆਨ ਦੂਤ ਜਮ ਦਲੈ ॥
Where the great and terrible Messenger of Death shall try to crush you,

ਤਹ ਕੇਵਲ ਨਾਮੁ ਸੰਗਿ ਤੇਰੈ ਚਲੈ ॥
there, only the Naam shall go along with you.

Only Naam can help you through this terrifying experience.

Anyways, back to friends. How can they be our true friends, when they themselves are stuck in this same cycle. How can they help you, if they themselves are trapped? Guru Ji says in Asa Di Var..

ਕਿਸੁ ਨਾਲਿ ਕੀਚੈ ਦੋਸਤੀ ਸਭੁ ਜਗੁ ਚਲਣਹਾਰੁ ॥
With whom should I become friends, if all the world shall pass away?

It is worth noting, that Guru Granth Sahib Ji is mainly written in rhyming couplets. However, this particular pangti is an odd one out. If you look at the structure of this shabad, you will realise that this line isn't part of a rhyming couplet. It is an individual line, as shown below..

ਕੂੜੁ ਮੀਆ ਕੂੜੁ ਬੀਬੀ ਖਪਿ ਹੋਏ ਖਾਰੁ ॥ ਕੂੜਿ ਕੂੜੈ ਨੇਹੁ ਲਗਾ ਵਿਸਰਿਆ ਕਰਤਾਰੁ ॥
ਕਿਸੁ ਨਾਲਿ ਕੀਚੈ ਦੋਸਤੀ ਸਭੁ ਜਗੁ ਚਲਣਹਾਰੁ ॥
ਕੂੜੁ ਮਿਠਾ ਕੂੜੁ ਮਾਖਿਉ ਕੂੜੁ ਡੋਬੇ ਪੂਰੁ ॥ ਨਾਨਕੁ ਵਖਾਣੈ ਬੇਨਤੀ ਤੁਧੁ ਬਾਝੁ ਕੂੜੋ ਕੂੜੁ ॥1॥

I feel Guru Ji has done this to put special emphasis on that line, to make us think about it slightly longer than the other lines. It shows the importance of this line.

In Salok Mahala 9, Guru Ji has pointed out what the worldy friends tend to do..

ਸੁਖ ਮੈ ਬਹੁ ਸੰਗੀ ਭਏ ਦੁਖ ਮੈ ਸੰਗਿ ਨ ਕੋਇ ॥
In good times, there are many companions around, but in bad times, there is no one at all.

Is that what you call a true friend? No.
But who will help..?

ਕਹੁ ਨਾਨਕ ਹਰਿ ਭਜੁ ਮਨਾ ਅੰਤਿ ਸਹਾਈ ਹੋਇ ॥32॥
Says Nanak, vibrate, and meditate on the Lord; He shall be your only Help and Support in the end. 32

A true friend is the one who will help us no matter what situation we are in. Who is this true friend..?

ਸਜਣੁ ਸਚਾ ਪਾਤਿਸਾਹੁ ਸਿਰਿ ਸਾਹਾਂ ਦੈ ਸਾਹੁ ॥
My Friend is the True Supreme King, the King over the heads of kings.

The King of kings; The ultimate being; Akal Purakh Waheguru Ji himself is our true friend.
May we never forget our true friend over the friends that will so easily leave us.

Waheguru