On a fixed gear relax your legs to coast or simply move your legs clear of the pedals. It is possible to resist the movement of the wheel but it is tricky and only safely done with toe clips and straps or those "clipless" cycling shoes. I don't like it, it throws me out of the saddle before doing any actually stopping.
Fixies and track riding is a whole different experience and culture. Because your legs are always moving it does drive to keep putting the power down subconsciously. Very tall gearing is used, almost always single speed unless you spend a relatively large amount of money for a special hub gear or a lot of time modding a freewheeling hub gear.
On any bike strapping your feet in does let you pull up as you pedal, but putting in more power means more effort and cycling ought to be fun and easy.