If u do a good deed to me, u'll want some kind of acknowledgement from me, so that it is conveyed to u that i really appreciated ur favour ........... but what if i go on to say, Forget It i m not thanking u, i neva' need ur favour. this shows that i didnt appreciate u helping me, and u will feel bad in the inside and wont ever help me again ............ its a natural trait for us to wish for an acknowledgement/appraisal for our good deeds.
So, as far as u r concerned, u'll only feel bad abt doing a good deed and probably no more than that. {Just keep on following me here}. But what if i want a favour from u again, Will u help me again?!! Most Probably Not, right? so, who is at a loss, U or Me? of course Me, 'coz of my unacknowledgement/unappraisal of ur 1st favour, i lost a 2nd favour from u ....... { i hope u r uptill here with me} ......... Now, What if i would have Thanked you for ur 1st favour? u'd have had felt good abt doing me a good deed, so u wouldn't turn me down for my 2nd favour. So it concludes if i would have just thanked u, i would have had gained more subsequent favours from u for the each favour that i thanked u for.
Similarly, ur thanks Won't effect GOD, but u'll be doing urself a favour if u Thank GOD for his unbound bounties on u, and it will keep u humble and u'll appreciate the bounties as well as ur life, from GOD. But, if u dont then u'll take all the bounties as well as ur life for Granted, be ignorant and arrogant abt the blessings in ur life, and wont ever be able to fully appreciate ur life and eventually will deviate from The Right Path.
So, do urself a favour and keep on thanking GOD, so that u'll always be reminded of HIM and HIS Bounties and u won't ever lose The Right Track of ur life. Thanks GOD (ALLAH) for giving me a chance to reply to u. Peace to All.