Sleeping in a bed that's just right for you and making sure that the cloth we wear isn't too tight matters. Trust me, playing golf with a sore neck and tight cloth feels like my body is strangled. But still, I believe a human is most vulnerable when comfortable...
Of course, this is to an extent and mostly applies in the mental aspect of things, but it's all relative.
Physically
Clearly, sitting on your couch and eating all the junk in the world that will drag your health into the abyss of diabetes, obesity, and all the health problems you can think of. Athletes train early in the morning and late at night, along with eating food that not too many enjoy making sure they reach peak fitness and health before their competition. Just cause they are athletes does not mean that they are the only people who do this, as you would know. Exercise and eating healthy, and just taking the time out of the day to get a little physically uncomfortable goes a long way!
Mentally
Now, this is a complex and big idea that not too many people may understand, but that is why I'm here to help and would like you all to lend me your ears... Comfortability in the mind has a lot to do with the physicality and vice versa as well but put those things aside for a second. By Mentally, I mean the ideals, values, curiosity, and mindset you have towards everything. And by comfortable, I mean the state of placidity and stagnation where there is no growth and fluctuation. When you become "Comfortable" and never challenge yourself the ideas you think are set in the world, you create a breeding ground for conflict and pain.
Just because you think that abortion is the cruelest thing in the world does not mean that the person next to you thinks the exact same thing. Just because your religion believes in one god, it does not mean the people in that corner over there believe the same thing.
We are all so different, and what seems so lost in this world is being able to work together through our differences.
Many of the conflicts in this world are because we see each other as lesser or better and can never understand that we are the same but have differences. Lashing out at each other because we think our own ideas are right.
And thus, don't be afraid to talk to people of different backgrounds and cultures and discuss topics that seem so sensitive nowadays. What's key in these interactions is to listen and understand their perspectives and whats shaped them. It is also more than appropriate to express your ideas and thoughts, and there you will find similarities and differences.
Challenge those set of ideas you have and stay as FLEXIBLE as you can. Be nimble, and even if this is uncomfortable at first, you will learn that you will form ideals through everyone's opinions and ideas.