Yeah, it really is worth differentiating between "a bit faster than an easy pace" and a pace which is a challenge to maintain over an extended period, but short of all-out effort. If I've made a good effort of the tempo section of a run, I find that the cool-down section is always run a bit slower than the warm-up, simply because I've stretched myself, so that my 'comfortable' speed is now slower. So start off really easy then when the tempo section starts, click into a different gear - but concentrate on running relaxed with good form. Good luck.