We should give thanks and praise to God since He created us and shepherds us. It is a blessing to know that the Lord never changes. In today's world, He is just as dependable as He was when He rescued the Hebrews from the Egyptians at the Red Sea. Our Lord also bestows blessings on us every day. Even difficult circumstances can be met with thanksgiving. 
This song of thanksgiving was written during the reign of David. Worshippers of Israel would process through the gates of Jerusalem to the Temple of the Lord with songs of praise in their hearts. However, the veil of the Temple has been torn in two, from top to bottom. This allows all who wish to come to worship at the feet of our God and Savior to do so.
All of these reasons make the Gentile nations and Israel jointly obligated to enter His gates with thanksgiving in their hearts. We are all invited to enter His courts with praise, giving thanks to Him and blessing His name forever. We are all called upon to accept Jesus Christ as our Lord and Savior, who has paid the price for our sins and has within Himself the Word of eternal life.

Dear Heavenly Father, Thank You for giving us the Word of Life in Christ Jesus. My praise belongs to You for making me Your people and the sheep of Your pasture by grace through faith. Thank You for being our Creator, our God, our Savior, and our Redeemer. Only You are worthy of praise and thanksgiving, and we bless and glorify Your holy name. My Lord, thank You for keeping Your promises and fulfilling Your Word and for Your lovingkindness enduring forever. 
In Jesus's name I pray. Amen.