If that is true, why pray?   

If everything is going to happen a certain way in a certain time, shouldn't we just sit back and let it happen, enjoying the ride?   

Pray without ceasing. 1Th 5:17 We ought to walk in awareness of the Holy Spirit in us such that all our thoughts are shared with Him and processed in accordance with His Word.      In so doing, we pray without ceasing.      Prayer is communication with the Holy Spirit.     Since we are in partnership with the Holy Spirit keeping the lines of communication open is critical for the successful operation of the partnership.      Think of how a singing duet must be aware of what each other is doing in order for them to hit the right note and the right syllable at the same time to produce harmony.      Praying is harmonizing with the Holy Spirit.

Why?   Does it make any difference?   I mean if God wants me to do well, it will happen and if he wants trouble to come upon me, it will happen.   

Calvinish is fatalism which i Satanic.   

Yes, our Lord could order everything to behave a specific way and that would be the end of it.   

But our Lord wants to partner with us.   

Granted, no scripture makes that statement.   However, the fact that our Creator interacts with us is a testament to the fact that He does not want to force us, but to work with us.   

The Lord does not move in mysterious ways.   In looking at the scripture we see the Lord working with various men to accomplish His will.   

God did not need Noah to build the ark.   He could have just levitated all those He wanted to save from The Flood.   

The Lord did not need Abraham.   He could have birthed Himself through any virgin at any time.   

The Lord did not need Moses.   He could have levitated them and translated the children of Israel into palestine.   

The Lord did not need David.   He could have dropped Goliath with a heart attack.   

I could go on, but the point should be clear.   Our Lord wants to partner with us to be and to achieve.