We all have a little bit of Cain in us. When things don't go right, or when it seems in general that God just isn't around. The story of Cain in the Bible discusses a more unfortunate aspect of human nature to discard God and rebel to one extent or another when things don't go right or if it seems God is unavailable. (Yes I know, the Bible doesn't overtly say Cain discarded God, but since he killed Abel I think we can safely say he discarded God for a certain amount of time.)
I sadly fell into that hole for a while (didn't kill anyone of course lol I know I'm a conservative blogger, hyperparanoid liberals can relax that my only weapon is my blog. XD ). On a serious note, many people fall into the hole. It is very unfortunate because the Bible is full of indicators that God is extant.
I'm going to talk about one of the more obvious ones. The State of Israel is perhaps one of the more overt indicators that God keeps his promises.
"36 You are saying about this city, 'By the sword, famine and plague it will be handed over to the king of Babylon'; but this is what the LORD, the God of Israel, says: 37 I will surely gather them from all the lands where I banish them in my furious anger and great wrath; I will bring them back to this place and let them live in safety."
"And I will bring them out from the people, and gather them from the countries, and will bring them to their own land, and feed them upon the mountains of Israel by the rivers, and in all the inhabited places of the country."
Now there's 2 miscellaneous issues that I want to address.
1) If God is the God of all humanity, why are the Jews the "chosen people?"
It seems to me that from a biblical perspective, that Author of History has chosen the Jews for a special place in eschatology. It certainly doesn't mean that God doesn't care for the rest of humanity.
2) Why is there suffering in the world?
Ever see a person who was pampered his whole life? The sad truth seems to be that the school of hard knocks to one extent or another is a necessary evil to turn boys into men. (That's just my own speculation by the way, it's not an opinion based on the Bible. Also, I'm not saying it is theeeeee reason, just one possible reason.)
One should not be deterred from coming to God for the forgiveness of human errors and for God's help. God does not demand perfection from humans, he knows we are imperfect people. He created us that way; like sometimes we get angry, or lazy, or jealous. When Cain's sacrifice failed, God did not say 'you are imperfect, so you are doomed, there's no hope for you;' instead, God invited Cain to do better. God's mandate to humanity is self improvement (not perfection). He wants to see humanity succeed.