How to maintain my focus on any Programming language

Hello Everyone,

I am one of the very good freelance programmer whose passion is to code, I have been coding for 4 years but my only problem is that i can't be able to work on any particular language for a long time and i am keep switching my languages.

I have worked on PHP, Java, Android, VBScript each for 4 to 7 months and then i switched , due to this i have no good experience in any specific programming language and this is my only concern.

In order to avoid switching programming language I need an idea to build since i have no idea for the app or website to develop i am wasting a lot of my time and I'm having a lot of stress everyday as what should i learn.

I need someone to guide me to keep my focus on one language and never switched it.
How can i do this ? How can i avoid keep switching my programming languages.

Here is some of the option i have considered lately, C#, Java, Android, Windows Phone Development, PHP

Could anyone please guide me through it ?

Thanks -