Why my android is slow?

Couple a days ago I tried to use my phone and it was so heavy and slow, this happened after I've installed few apps.

I tried to search on google. If there is some problem with Handcent but couldn't find anything about it. So I've changed my search query and got to my requested answer from http://myhtcdesire.com/tag/slow:

Before I get into this I want to make one thing clear: it’s not bad to have a task killer installed for the purpose of checking what’s running or to close unnecessary apps, but if you have it make sure the task killer itself isn’t running in the background.

Ok, so a lot of people with their new Desire have been recommended to install a task killer.  Here’s a few reasons why you don’t need one:

  1. The way Android OS works is that when an app is in the background then it’s as if the app is frozen and not really running.  The exception being apps that need to run in the background such as feed readers, Twitter clients and so on.  Having apps in the background that aren’t doing anything is therefore not a problem.  The ones that are (Peep, Stocks and so on) you can just change their update frequency to something higher so they’re not running as often.
  2. The memory management of Android makes sure you always have sufficient free memory. If the available memory falls below a certain threshold your phone will automatically close older applications.  Even though this wasn’t too efficient on the Hero, it’s far better on the Desire which has more initial memory to work with.
  3. Task Killers themselves use up system resources constantly and in turn use battery life, not to mention that it’s trying to access ALL the other processes.  Many users have reported an increase in battery life when they don’t have a Task Killer running
  4. Some task killers will make Sense laggy.  Lagginess is a common complaint from Task Killer users.  It keeps trying to access the Sense process and causes it to lag.
  5. Certain apps restart anyway.  HTC Apps like Stocks, Peep and Footprint will restart themselves whenever they’re closed.  This restart process might cause your phone to lag for a second, use up extra battery during the initialisation process, and so obviously closing such apps has done more bad than good.
  6. The Desire actually has enough memory and processing power to handle many applications being open.  If it’s not broke then don’t fix it, right?

If you insist on having one installed then make sure it’s not always running.  When you select apps to close, make sure the task killer itself is included.

and from here http://forum.swype.com/showthread.php?2660-HTC-Desire-HD-Swype-very-slow-to-locking-up-the-messaging-system-after-1-day:

This used to happen to my Desire HD also. I think its just a general Desire HD problem that seems to affect some devices. Swype just seems to exacerbate the symptoms, as I only started noticing it after installing Swype also. My whole device used to slow down after a day or 2. The method I tried to resolve my problem is below.

Some Desire HD's seem to have a problem with one of its processes hogging upto 90% of the CPU at any time. The process is /INIT its a core android process so cannot be prevented, but there seems to be a simple fix for the problem, On your phone go to: Menu/settings/applications/development/ and turn on Usb debugging and restart the phone. See if this fixes your issue. Usb debugging doesn't seem to affect any other functions on the device and you can still connect it to a PC, the device will just try and install some extra drivers when you do. A thread with all the details can found over a xdadevelopers

It may just be that your cache or data is corrupted, try going into the manage apps menu and find swype and click the clear cache and clear data buttons, reboot and see if it works. You can also try completely uninstalling the application and installer and reinstalling them again.

Hope this helps.

So I`v followed this recontamination and found out that WatchDog app was sucking my phones memory. After I`v uninstall-ed it and restarted my phone it was fast like a Cheetah‏ ;)

Hope I helped you,