When you are in a bad trade and you have not been able to get in to proper trading despite all the dedicated practice, it is quite natural for someone to get irritated.  You did believe that your trading plan was so great that it would win at all times and not fail at all; however, now you tend to realize that there is yet another methodology that is better than what you are doing now.

You are just annoyed and you had a pay a big price to know that there is yet another better method.
You decide that you will change the way you move things in your trading.  You form a new rule or you tend to change your old plan so that such a rule can permit you to capture the trade that you happened to miss.  Well, this bit of modification can also be a mistake, because the new variation you introduced to your trading plan can work the other way round in that your new varied approach can make you to be stopped out with less or no profit at all.

Immediately after you leave the trade per plan, the prices might increase and it will probably move to the location where you actually were staying in before you changed your plans.  Again you regret for having changed your plan. 

And this little move leaves you thinking that you were an idiot to have changed the plans.  At this point in time, you start believing that there is something wrong with the way you are doing things.
Either your rules were wrong or your planning was wrong or the kind of plan you choose to execute was wrong. 

You need to learn about situations in more depth if you should know when you should actually change what you are doing. 

Sometimes you plan would be really fine and it could have been just that it was not okay for a couple of times.  There is no plan that brings in 100% profit. 

So, you should have tolerance threshold for loss rather than changing every plan you make with every loss.