décider v. se décider

[alan gould]

I decided not to go.  J'ai décidé de ne pas y aller.

but 

J e n'arrive pas à me décider à y aller ou pas.  

Is this the only time when you would use the reflexive?: 

I can't decide whether to -  Je n'arrive pas à me décider à

[alan gould]

I found the answer.  the reflexive is used meaning "to reach a decision" so you have to be considering two or more options.    

[Neil Coffey]

Yes, "se décider" implies a more 'considered' or 'determined' decision (in English, something like "I made up my mind to...", "I took the decision to...").

As you observe, it is used with "à", whereas "décider" on its own is used with "de".