"And let us consider how to stimulate one another to love and good deeds, not forsaking our own assembling together, as is the habit of some, but encouraging one another; and all the more as you see the day drawing near."
Christians ought to desire to be together, especially on the Lord's Day. The reason to assemble is not for an empty ritual but to show love to God and the brethren.
The Christians being admonished here in Hebrews were the ones that didn't believe in meeting regularly with other Christians. Perhaps they had a disagreement with someone or were disillusioned by hypocrisies or sinfulness in the Church. However, in the New Testament, these relationships were important and disagreements or misunderstandings had to be worked out. This is true today as well. A Christian is defined by God's Word and there are no lone Christians in the Bible.
"So, as those who have been chosen of God, holy and beloved, put on a heart of compassion, kindness, humility, gentleness and patience; bearing with one another, and forgiving each other, whoever has a complaint against anyone; just as the Lord forgave you, so also should you. Beyond all these things put on love, which is the perfect bond of unity." Colossians 3:12-14