Thankfulness seems to be a running theme throughout the Bible. We see Moses give thanks to God after the parting of the Red Sea. (Exodus 15:1-19) We see Jesus give thanks to the Father for hearing Him just before Lazarus is resurrected. (John 11:41-44) And one of the Psalms says, "Give thanks to the Lord, for He is good, and His steadfast love endures forever." (Psalm 106:1) We're told by Paul to "give thanks always for all things to God and the Father, in the name of our Lord Jesus Christ." (Ephesians 5:20)
In my experience, I've found that following this advice is extremely beneficial. Thankfulness makes hardship easier to endure. It makes it harder to take things for granted. It helps me keep my priorities straight to remember to be thankful to God for what He has given me, since I remember that all I have is a gift from Him and ought to be used for His will. A lot of times, it even helps diffuse anger to remember to be thankful for whoever or whatever you're angry at.
What's something you're thankful for today?