You have to fill the gap with something else enjoyable/stimulating.

Also, often people find they enjoy some of the activities they would be doing all along without the drugs,

ie. Hanging out with friends, lying have passed out on a couch watching TV / playing video games / staring at the ceiling listening to music, sex, bumming cigarettes, hustling for money, going to dangerous places / doing dangerous things, committing small time crimes, alienating family, ect…

You can enjoy all these things while sober… no need to be boring ;-)