Credit scores are fascinating and not always logical. This articles captures a few of the common misconceptions. Keep that older credit card open, even if you don’t use it, both to improve your available (unused) credit, but length/age of credit helps your score too (not mentioned in the article).
http://www.huffingtonpost.com/2014/12/14/credit-score-myths-_n_6296012.html?cps=gravity