We have a Predator

"Your enemy the devil prows around like a roaring lion
seeking for someone to devour." 1 Pet. 5:8
This predator, Satan, is constantly trying to devour God's family. In nature, predators target the weak, the young, the straying, the sleeping, and the unalert. It is no different in the family of God. The vulnerable ones: the young, the weak, the straying, the sleeping (spiritually speaking), and the unalert are easy prey for the devil. That's one reason why fellowship is so vital - to protect one another from predators.

The ingredients of fellowship
To a large extent the preservation of the Church depends on a strong connection between its members. In fact God cautions people not to become disconnected: “Let us not give up meeting together." Heb. 10:24 I have often heard this phrase expressed this way:

“Forsake not the fellowship”.

I like that word, "fellowship", and I think it fits. The word, "fellowship" has a much richer meaning than the word “assemble” or “meet”. Fellowship involves close community, participatory relationships, common sharing, unity, agreement, and being closely knit. There are many scripture verses that describe the various ingredients of fellowship. Romans Twelve lists some; ex: prophesying, serving, instructing, encouraging, contributing to the needs of others, leading, showing mercy, hospitality, empathizing, forgiving ...feeding the sheep... and there are many more in the Bible.
Healthy fellowship includes all these ingredients. They help to strengthen the flock of God's sheep and protect it from predators.

"Love always protects." 1 Cor. 13:7
The phrase "forsake not the fellowship" is extracted from the following verse. Notice the other components surrounding the phrase:
"Let us consider how we may spur one another on toward love and good deeds.
Let us not give up meeting together (forsake not the assembling.... KJV)
as some are in the habit of doing,but let us encourage one another
- and all the more as we see the Day approaching." Heb. 10:24

From this verse we see that assembling together had a very specific objective: to spur one another to love and good deeds, and to encourage one another to grow strong in the faith because there will some day be a Final Judgment.