It isn't "they" that says it. It's God. He says his "yoke is easy and his burden is light." He also says that "many are the afflictions of the righteous, but the Lord God delivers them from them all." HE ALSO says, 'IN EVERYTHING give thanks..." Everything. Not just the easy times, but especially in the hard times. He also "causes ALL things to work together for good for them that love Him and are called according to his purpose." That's in the bible. Look at biblegateway.com if you don't believe me. ALL things, means everything-even the ugliest most painful parts of our lives.
Everyone suffers loss. Everyone goes through storms. Everyone faces difficulties. Everyone has issues. Everyone has problems. Death is a part of life, and as painful as it is to suffer loss (Even Jesus wept!), we have to accept it as an inevitability instead of being bitter towards God for it. Death happens. Everyone who is born, dies, with only a couple exceptions in the bible. Being bitter that people have died accomplishes nothing. Would your parents want you to continue to mourn them, or would they want you to live your life as if they were watching? My guess is the latter. Does that mean it is wrong to miss them? Of course not. That's quite natural. My father died last February-a day before Valentine's Day, while I was in the middle of aquiring my Associate's Degree finally at the age of 33. I am the one who helped confirm to my mother that he was indeed dead. My grandmother died in 2008 while my fiance was in jail because one of his babies' mothers put him there accusing him of something really horrible that wasn't even close to true. I wasn't able to be at her side because I was dealing with that, even though we're in the same city.
Nowhere in the Bible does it say that we are going to know WHY we go through anything. God only demands that we trust Him to bring us through it. Is it easy? GIRL??? Of course not. We are human. It is in our nature to question whether or not we can trust...However, God is perfect, and he is perfectly trustworthy. He sees you where you are and meets you in the midst of your pain. You just have to choose to trust Him. Make a daily concerted effort. Pour out your heart to him and tell him you are angry that he "took" your parents from you. Then ask him to forgive you for being bitter about it. Then...CHOOSE to trust him, even if you have to choose to several times a day. It is not easy at first, but then...things start to fall into place. Faith in him is a day by day thing. A relationship that is one-sided often doesn't work. The same goes for a relationship with God.
Hugs. Keep your head up.