Change takes time and persistence. It took a long time to entrench your unwanted behaviors, so it takes a little while to undo them (perhaps 30 days for lasting change, but you can start to feel a healthy shift sooner, if you’re consistent). Sure, change can be painful - much like the pain you feel when you start working out. When you are consistent and persistent, though, the muscles get stronger, and it becomes not only easier and less painful to work out, but part of your muscle memory.
However, it will be far more effective to go slow and take baby steps than to overdo it. How many times have you charged full force into a New Year’s resolution or workout regimen only to burnout, guilt-trip yourself and feel like a failure (which causes the guilt and stress that can trigger unwanted behaviors)?
Rather than starting to work out three hours a day, six days a week (then quit after a week), start with one hour a day for two days a week. Then, slowly increase to three, four or five days a week, depending on what works best for you.
Give yourself permission to go slow, and know that setbacks are part of the process (but less likely if you pace yourself). We may have to do the opposite of our urges for a while, and fake it until we make it, but the human brain is much more plastic than previously believed.
Know that if you patiently and persistently practice your new behavior and neglect the old behavior (use it or lose it!), your brain will create its own “muscle memory”, and the change you sought is now automatic and stress-free!