By making it small enough that you can't talk yourself out of it. The runners who stick with it aren't more disciplined — they've just lowered the bar to entry.
A few honest things that work: keep early runs short and easy enough that you finish wanting more, not wrecked. Put runs in your calendar at specific times rather than "sometime today." Lay your kit out the night before. And separate the decision from the mood — you don't have to feel like running, you just have to start; the motivation usually shows up once you're moving.
Most importantly, expect to miss some. Missing a run isn't failure — it's normal. Consistency isn't never missing; it's not letting one missed run become three weeks off.