A former teacher of mine used to say that an out of tune note, even played in the right place at the right time, is still a wrong note. Not only do you have to be able to recognize the difference between in- and out-of-tune, but you also have to be a skilled-enough technician on your instrument to be able to bend the pitch to your will.
The first question you should be asking yourself is, “what does it mean to be in tune,” and the second, “how do I play in tune?”