Not everything is best, but everything is for the best: Pesach

At my house on Pesach, there are two predominant arguments:
"CAN I EAT THE PEANUT BUTTER OR DOES IT COUNT AS KITNIYOS?" (Answer 1: I've always been using peanut oil...Answer 2: Peanuts are kitniyos, Leora dear....)
We decide that yes, it is kitniyos, and no, I cannot have the peanut butter. I resign myself to matzo pizza.
But on a more serious note, there is another (arguably more important) predominant argument in my house and Pesach, and that is:
"WHY ARE WE THANKING GOD WHEN HE IS THE ONE WHO MADE US SLAVES IN THE FIRST PLACE?"
It is a fairly common idea to think that a quick "thank you" to God would be enough. He brought us to Egypt, made us slaves, and then He took us out. So, um, thanks, God for that? I appreciate Your kindness is releasing me from the bondage You put us into, but, um, is this whole Seder really necessary? (I don't know about you, but my Seders start at eight and end around one in the morning, which may seem excessive, but I believe is the perfect Seder length.)
Some say no. 
I say yes, it is necessary.
God may have put us through this slavery, but we did not come out of it as the same Jews we did before. On a material level, we left Egypt with gold and many of the Egyptians' riches. On a spiritual level, we left with a greater devotion to God-- after all, we had the courage and strength to still believe in Him while under great duress. We were different Jews coming out of Egypt than coming in. But for this we should thank God? We should thank God for putting us through the ordeals in Egypt in the first place?
I recently faced a painful rejection and was absolutely devastated. I was, frankly, angry at God and much of the world around me. Before Shabbos, I have a tradition of sending my best friend in Israel an email about my week and the weekly parsha. That week, I sent him a short email, consisting really of three words (two in Hebrew): "I was rejected."
He immediately responded, saying to me the usual things, which were only somewhat comforting at the time (i.e. it's not the end of the world). He did, however, say to me one thing that struck home. Hakol lo tov, aval hakol le'tova, he said, translated to "not everything is best, but everything is for the best." This made me wonder and remember that this hardship was not a coincidence, and that it was part of something greater. This "something greater" was God's plan for me. I turned away from this hardship with a renewed sense of purpose, feeling like Julia Roberts in Pretty Woman ("Big mistake! Huge! I have to go shopping now."), knowing that this rejection, this kick-in-the-gut feeling only made my gut stronger and more able to forgo peanut butter during Pesach (and, of course, go to college, get a job, do incredible things in life, etc.)
Hakol lo tov, aval hakol le'tova.
So am I saying that slavery in Egypt was a good thing? Not the slavery itself. I'm just saying that we give God thanks on Pesach for making us a stronger people through this experience as slaves. We emerged from it wealthier in riches, more devoted as a people and stronger in spirit, and for that, we thank you, God, this Pesach.