It depends on the loss and the frequency of its occurence in your trading.
If you have losses systematically, then you've got to pay attention to them and get to the bottom of the reasons for them. I feel that one of the key things in trading is that yo should constantly challenge your trading strategy and find the ways to make it better and perfect (although perfection is impossible in trading). Every deal should be examined in the detailed way and you have to analyse the reasons for this or that outcome. If your strategy works well, then you'll have more successes than losses, but even in this case you should have a clear-cut idea of which factors led to the failures. Only by doing these steps can you make your trading improve and your trading results develop. If you have more losses than profits, you've got to analyse your decisions. Perhaps, you misuse some of the indicators or you should be more attentive to the entry/exit points in your trading or emotions play huge role in your trading and so on. I goes without saying that some of the deals will definetely be unsuccessful because the market is rather unpredictable, so, more often than not, you can do everything right but the market decided to go in the opposite direction.