What's harder? To constantly workout, or to constantly be at peace within? I think it's subjective, but i think also that for the majority of people including myself, it is harder to constantly be at peace within. Working out is something you do and then your done until your next session. Being at peace withing is something that has to be constant, something you got to preserve at any moment, something that might take a lifetime to achieve. A lot of people die without being at peace within themselves. If you don't accept the fact that your body will break one day, you're not at peace. I don't consider myself a spiritual person, but i like spirituality, i think spirituality can bring a lot of peace within. If everything in your life goes well, been well from your baby years to now, working out could seem harder. But if everything went well for you, it does'nt mean it will continue to go well and then, that peace might be challenged.
I think that for most martial artists, and that is coming from a non martial artist, i think it's harder to find constant peace within than getting proficient at combat. That's why you will see a lot of fighters who cannot make the transition from being a fighter to becoming a true martial artist because they can't find that peace. A fighter might think he's at peace kicking asses here and there, but they be lying to themselves. You can't really be at peace if you need to hurt people. That's why you will see a lot of people on steroid, they can train but yet they don't have enough peace within to train naturally.
I think that there's different level of internal peace. You might get to level 5 but it doesn't mean you can get to 10, meaning being in ultimate peace. I think a 10 would be for a very few people, you might get the chance to feel that 10 in your lifetime in a couple of occasions but to stay at that high level would be very difficult, way more difficult than lifting weight since a training session doesn't last 24/7 and 365 days a year. Personally i think i'm approximately at 7, sometimes 8 and sometimes i can go down to 5 on very bad days. I know i can get better in my workout, but i know i can get better at being at peace within myself too. To me, fitness achievements ain't worth shit if you can't be at peace within yourself. You can be the world champion in something, but if you're not at peace within yourself, and dissrespecting other beings, then your title ain't worth shit but ego. We need balance in this world, as human, as animal, as life. If we don't find balance, something else will find us; hate, destruction, anarchy, in a simple word; chaos. The challenges that life brings alone in itself are tough enough, we don't need additional negativity to make it harder. So on that last note; hope, optimism, acceptation, forgiveness, efforts, dedication, discipline and a thirst for learning new things are keys for a better life, for being healthy and at peace within until our souls finds its next path.