I believe born again includes sanctification unto justification (1 Cor 6:11). Many have the idea that sanctification is an ongoing process, but it involves a single act which never needs to be repeated. Same as salvation, which is eternal, or it isn’t salvation (Heb 5:9).
The believer is maturing or being conformed continually but it's not through sanctification, which has already taken place, "For both He that sanctifies and they who are sanctified are all of one" (Heb 2:11).
Everything from Christ (sanctification, justification, righteousness, holiness, etc.) is fully supplied to the believer (2 Pet 1:3) and it's now a matter of the maturation from these things. They are all-inclusive in our salvation which now has become a matter of "working out your own salvation" (Phil 2:12); again, not to produce these things (already supplied) but to mature in them. The idea of "working out" has to do with figuring out, as in understanding by learning an equation which has been solved.
Once the believer has been "set apart" (sanctification), it becomes solely a matter of conformation (Rom 8:29) and transformation (Rom 12:2)--which are ongoing processes by the Spirit of God.