Sleeping on the streets isn't that tough if you can keep these basic things your priority:
1. Keep clothed and carry a backpack, rucksack or bag with a cheap surplus sleeping bag, cheap foam mat and some spare clothes for sleeping in.
2. Eat 3 meals a day however you have to.
3. Stick to yourself and avoid spots that are frequented by homeless people. You don't need to be worrying about getting ass raped, beat up or getting jacked this way.
4. Try to bath every other day and use copious amounts of soap.
5. Stay away from the drugs.
Those are the most basic and important things to keep on top of.
It's not that hard really. Sure, you don't have many luxuries, but you're still probably living easier than people did a 100 years ago.