I'm usually a well rounded player but I'm bad at two things

1.) I play too fast

2.) I'm bad at judgement I don't know if it is worth it to trade pieces

Could you please give me sugestions

1.) Slow down

2.) Slow down

Honestly, though, #2 can be a real challenge.  Understanding good vs. bad minor pieces, and when you're able to trade down to an advantageous, even won, endgame would be a good place to start I think.  Sillman's "How to Reassess Your Chess" gets into some of these assessments in a fair amount of detail if you're looking or reading material on the subject.

thanks!

Regarding trading pieces, I really liked these columns by Dan Heisman (from his monthly Novice Nook column).  They all have to do with evaluating when exchanges of pieces are and are not advisable.  In order that they were written:

A Counting Primer (April 2002)
The Most Important Tactic (December 2003)
Is It Safe? (June 2006)
The Two Types of Counting Problems (April 2007)
Counting Material (December 2010) 

The first one is a must-see, as it introduces the basic ideas of what needs to be considered when examining whether to initiate an exchange or a series of exchanges.  However, it also has an error in the first diagram on page three, and Heisman has the correct diagram here.

The full archive of Heisman's Novice Nook columns, presently chronologically and also grouped by subject, can be accessed here.

Wow, I linked to those articles cystem_Phailure.  Heisman has some excellent stuff.  That should be required reading, linked on the main page or something.

Honestly, I don't know what to say, but for N vs. B, general rule: The Knight is superior in closed positions, the Bishop is superior in open positions.

Shhhhhhhh...

It really depends on what kinds of bishops they are.  Episcopal, Catholic, etc.

Yes, in a tightly locked up position, a Bishop can be really constrained and not worth very much for quite a few moves into the future.  In that situation, giving up a Bishop to get the other person's Knight may well be advantageous, rather than just an even exchange.  But you need to be able to use the swap to quick advantage, because if the game lasts to the point where the board is much less populated, the other fellow's surviving Bishop pair will become more and more important and powerful against you.

 My old coach had a simple but effective method to help with moving too fast:  sit on your hands!  Literally - tuck your hands under your butt so you can't just grab a piece (or the mouse), and when you want  to move, remember why you are sitting on your hands and look again!

As to exchanging, there is one rule:  does it bring you advantage?

Unless you gain something positive by initiating the exchange, don't do it - leave it for the opponent and improve the position of another piece or pawn instead.  If allowing the opponent to make the exchange is bad for you, you must decide whether to exchange yourself or retreat and avoid it.  Which to do?  Use the same method - which benefits your position the most or harms it the least?

I really like the Novice Nook column.  It's too basic for better players (hence the name of the column), but for me it's usually just the right depth-- reinforcing some things I know but don't always keep in mind, introducing tips and concepts that are new to me, and discussing ideas and lines at a level of detail that nicely matches what I'm willing to work to follow closely, as least as far as chess is concerned.