Life's Philosophy?

I am gonna state the obvious now.In life we go through ups and downs.It alternates between each other to so called 'balance' the ying and the yang.
I know about this whole balancing thingy but WHY do i have to go through so much downs at times?Is it really that bad to always have fun and be happy?Does life really have to be THAT complicated?
Now,in my life,when does this 'ups' occur and when does the 'downs' do?
Ups occur when i hang out with my friends,doing very interesting things together,laughing and not a single one is on a 'turn off' mode.It also occurs when I have a great time with my mother and my family.When i can just sit and talk with them,spend time with them,i feel the greatest joy and satisfaction.Then,there are those times when i do well in my studies,or some sport or something is accomplished,it always makes me feel so good.The thing is,why won't these things just stay and be like that forever?Why must there be something or someone always ruining it?
The 'downs'.When does it happen?Simple.When someone turns me off by saying something i hate,DO something i really hate and just make me go mad!Then there is the family issues that no one seems to be able to avoid.The thing is,I don't only feel mad,it also makes me sad,it's a terrible feeling that is undescribable.There will be THAT feeling that my heart feels.A void,where something feels amiss and just hurts so much.
God enlighten me.
Show me a way to overcome this 'downs'.
Guide me to a healthier life cause this feeling that I am feeling now hurts,bad.