Luc, you can't build a solid brigde without solid foundations. Right now you are at the stage of surveying the ground. I have been training for 3 years now and feel like im at the stage of boring that first hole into the ground to lay my first support strut.
When you were playing with your friend, you were probably (i would assume) going for a certain technique(s) to the detriment of others, this is something that EVERYONE does to begin with (usually its their favourite technique they go for first) relax and look for his balance first, then something will come to you (hand/head/arm/leg etc).
As for attacking first, when we are told not to attack first it think this means attacks which compromise our balance e.g. huge punches where we have to clear a lot of space to make them connetc. Alos, it comes from an idea of 'if we dont attack first, and the other side doesn't attack then there is no physical conflict, and that's the best way of all to avoid injury to both parties. A nice idea, but not always practical, so next time you and your mate have a bit of a play, aim a few quick punches up and down his body while you move into him to take his balance. balance is the Ki (crap pun i know, im very very sorry
Just have fun training, pretty soon you will notice the changes and the sublties of your technique.