When Hashem told Avraham Avinu that He would give his children Eretz Yisrael, Avraham asked "Bama aidah ki irashena - How do I know I will inherit it?" Hashem replied, "You should know that your children will be strangers in a land not theirs, and they will be enslaved and tortured for 400 years, and afterward they will go out with great wealth... and the fourth generation will come back to this land, etc...
There are two very strong questions here:
(1) What was Avraham's question? Did he not trust Hashem?
(2) How did Hashem's reply answer his question?
Says the son of the Ba'al Hasulam (Rav Baruch Shalom Ashlag in his Ma'amarim) that when Hashem told Avraham that his children will inherit Eretz Yisrael, this is not referring just to a physical land, but rather to the great spiritual light of "Eretz Yisrael": 'Eretz' is from the lashon "Ratzon". 'Yisrael' comes from the words "Yashar E-l" - that everything we do is for Hashem's sake. This means that Hashem was telling Avraham that his children will one day inherit the great light of being true servants of Hashem. When Avraham replied "how will they inherit this?" he meant to ask, what "need" will my children have for these great lights; for these great gifts; for this high level? In other words, there can never be light without a vessel for it. You can't fill a cup that is already full. If Hashem is promising such great gifts, Avraham Avinu wanted to understand how his children would develop the vessels for such great light?
To this, Hashem responded that they will be strangers in a land not theirs, and they will be enslaved and in pain, and only AFTERWARD will they go out with great miracles and great wealth, have the vessels to receive the Torah, become true servants of G-d, and to come back to the land of "Eretz Yisrael".
Without the darkness, pain and servitude of Mitzrayim, there would have been no need for the great revelation of the makkos, of Kriyas Yam suf, etc... and no "vessels" for Kabbalas Hatorah, where we finally became G-d's servants instead of servants to Pharaoh. If all had been fine and dandy, if Avraham's children would have continued the tradition of the Avos and had riches and wealth and remained in Eretz Yisrael instead of going down to Egypt, then we would have never had the vessels to become the "Nation of Hashem".
(This is also perhaps the reason for all suffering that we undergo in this world. For example, why was Dovid Hamelech's life was so full of suffering and strife? What did he do to deserve such "redifos" all his life? In order to bring out the David Hamelech that we know, in order to bring out all of his beautiful Shiros of how "Hashem saved him for his enemies and from the hands of Shaul" etc, etc... there had to be vessels for this great light.)
Our addiction makes us "strangers in a land not ours". We don't want to be here. It is not the "real" us. We are enslaved by it, and pained and tortured... sometimes for what seems like 400 years... but Hashem is mechashev the "Ketz" and knows our breaking point. He is waiting for us to develop the vessels for His true salvation, to enable us to become His true servants. This is perhaps the main reason Hashem gave us the addiction in the first place.
Let us use it for what it was given to us for, i.e. as a spring board to reaching a true relationship with Hashem. Hashem is awaiting our cry - "vayi'anchu b'nei yisrael min ha'avodah, va'ta'al shavasam el Hashem... va'yeda Elokim - and the Children of Israel sighed from the heavy labor, and their supplications went up to Hashem.... And Hashem saw the Children of Israel, and Hashem knew.