Sometimes your phone will be slow. It will not function much faster like it did before. There are reasons why the phone would be that slow. Either the phone does not have a lot of installed RAM or the phone memory could be full. When your phone memory is full due to many applications installed or due to too many media files, the best way you can make faster again is for you to delete all the apps that you do not really require. This way, the phone will have quite some memory available for it to run spy apps.
The next thing that you can do to make your phone much faster is to clear the cache. This means that there are temporary files that are stored in the phone and you may not actually need these files. As such, you have to clear this cashed data so that some memory is released for the phone to work much better.
It would also be a good idea if you can scale the use of widgets and live wallpapers. These take up so much memory in your phone that it ends up being slow. The scale of animation in your phone means that it has to be slow at some point. If these animations can be reduced to the bare minimum, then you can be sure that your phone will be fast again.