"A journey of a thousand miles begins with a single step."
No matter how large the task, no matter how far, how big, how insurmountable something may seem, it all starts with just one step.
Break down your journey into smaller, more manageable parts. Set smaller goals as part of a big goal or "journey." This could be simply showing up at the gym for a workout, or even as far as signing up with a gym. Or it could simply swapping out soda for water or another healthier behavior.
Just keep taking those steps towards success.