First things mean a lot to God and men

Revelation 2:4 Nevertheless I have [somewhat] against thee, because thou hast left thy first love.

God takes first things very seriously. That's is why there is the law in Bible interpretation called the law first mention of a word in the Bible like grace. The first mention of it, sets a precedence for other times it appears in the Bible. 

Even to men, first things are very important, it's never easy to forget them. To men, it is said the first impression makes a lasting impression. The first time you came to church, the usher who welcomed you makes you either stay in the church or leave it, the first birthday of a child is usually made so big because its simply the first if it's kind. Some have many unsuccessful attempts to get children so the day they give birth and the child makes one year is a big celebration to them. I also recall the first time people celebrated my birthday.  Hardly did anyone celebrate me before but that day was quite remarkable. Whenever I look at the pics of that time, I get fresh memories of it. Nowadays it's a common thing to celebrate birthdays but always the first one stands out. The first night of a wedded couple is hard to be forgotten, the first service or launch of a church etc.

Why am I saying all this, that just as first things matter to you, they matter to God also. For example the Bible talks about the first love, first born, first fruit, first converts, God's first visits to man on the earth in the garden of Eden, the first visit of His Son and the Holy Spirit on earth too were remarkable. All these are key in the Chirstian faith. 

Apply your heart to understand first things in God's Word and draw great lessons to apply them in your life.