“Not forsaking the assembling of ourselves together, as the manner of some is; but exhorting one another: and so much the more, as ye see the day approaching.”  
Hebrews 10:25

He says as the day approaches, one thing you should do much more- that means increase the frequency of your doing it- is ensuring you are always found in the assembly of the brethren, being exhorted by the word of God. There is a reason for this:
“For if we sin wilfully after that we have received the knowledge of the truth, there remaineth no more sacrifice for sins,”  Hebrews 10:26
God structured the assembly as a guide against sin, this is clearly seen also in Hebrews 3:13-
“But exhort one another daily, while it is called To day; lest any of you be hardened through the deceitfulness of sin.”  
He is saying that the assembly was set up to guard against any Christian being hardened by sin to the point where he/she does wrong and has an excuse for that wrong with boldness.
He had said:
“And because iniquity shall abound, the love of many shall wax cold.But he that shall endure unto the end, the same shall be saved.” Matthew 24:12-13
So many people would get to a point- and we are seeing it now- where they wouldn’t even know or believe in a clear cut different between sin and righteousness; they would make excuses for sin; rename sin so it can be satisfactory to them, and God says believers would be affected unless they increase their frequency of being amongst the brethren because on that last day “it was popular”, “I didn’t know” would not count.
This is the period to be found in church, in a cell, while satan is working to make many fall away, those found in the house of God would be equipped in righteousness!