The question: How does one enforce self discipline on him/herself if they aren't strong in discipline?

The Answer: Self discipline is real, but it has more than one source.

Here are a couple of my thoughts:

1. Self discipline can be acquired.
If we realize that we are not that strong in this area than we need to admit it and seek the trait.

2. Self discipline is not "self" discipline at all.
This trait is given to us by God, He has the power to strengthen us in this area if we ask. 2 Timothy 1:7

3. Self discipline is stronger when fully surrendered to the leading of the Holy Spirit.
Galatians 5:22-23

Mastering this trait pays HUGE dividends. This is a practice that God has been working me in all of my life. One, thing that I have realized is that if I just give up my selfishness and allow God to run my life--self discipline becomes a lot easier. Almost effortless.