David loved the Lord. Despite his many sins, he was described as being a "man after God's own heart." [1 Sam 13:14] Throughout his years as king he wrote a number of psalms expressing his dependence on God, he love for God, his faith in God, and the comfort he found in God, among other things. In the 122 Psalm, David expresses his joy over the opportunity to worship God. Just the invitation to worship made him glad.
What is our reaction to this invitation? Some share David's sentiments and jump on every opportunity they have to enter the house of worship to spend time with God, while others see it has a chore. They see it as something that HAS to be done, but they'd rather be anywhere else but worship. They take advantage of the smallest opportunity to miss worship, such as a headache or going to bed too late, and delight in the opportunity to finally sleep in, but is that an appropriate attitude toward God?
Yes, faithful attendance in worship is something that is required of us [Heb 10:25], but that wasn't David's motivation for worship, and it shouldn't be ours. Do you spend time with your spouse because you "have" to (sadly, some might say yes...)? Do you watch the Super Bowl because you "have" to? We find time to do the things we love. We plan around them, reschedule smaller priorities, and overcome minor infirmities such as headaches to spend time doing the things we love, and worshiping God should be at the top of that list.