hort answer is - never trade without SL and I'm sure many more people will agree. Some people (including me) use SL to get feedback from the market to know whether the setup was right or wrong. For example I'm a price action trader, if I see a "pin bar" I put my SL just above high (or low). If my SL is hit I immediately interpret this as market telling me "hey, this setup is invalid, market does not want to go that direction!" However you really want to include a method to trail your SL into your trading plan. That way you might exit the position at break even or some profit in case market turns against you. There are many ways to trail your stop, look them up and pick one that looks nice.

It is very risky to trade without setting SL. It could endanger your trading account.