You are there for your Sisters--the Sisters are not there for you. You must be ready for any sacrifice--so to say, to be eaten up by your Sisters. You may sometimes feel great loneliness--but this is one of the sacrifices you can make for your Sisters. It often happens that those who spend their time giving light to others remain in darkness themselves.

(Blessed Mother Teresa, Letter to superiors, Come Be My Light, p 248)

Of [my] free choice My God and out of love for You--
I desire to remain and do what ever be Your Holy Will in my regard. ...
Even if I suffer more than now--I still want to do Your Holy Will.--
This is the dark night of the birth of the Society.--
My God give me courage now--this moment--to persevere in following your call.

...

Today--my God--what tortures of loneliness.--
I wonder how long will my heart suffer this. ...
My God, give me courage now to fight self and the tempter.
Let me not draw back from the sacrifice I have made of my free choice and conviction.--
Immaculate Heart of my Mother, have pity on thy poor child.
For love of thee I want to live and die an M.C.

...

The more the work is spreading the more clear it becomes [it is] His Will.
Soon it will be one year [since she had left Loreto]--
though there has been plenty of suffering and tears,
there has not been one moment of regret. I am happy to do God's will.

(Blessed Mother Teresa, Come Be My Light, p 134-136)