Something I've found to help that is to break a longer task (like posting a CS) into smaller single-step tasks, making it seem less daunting.
[hider=Like so]I need to make a CS. (this is an actual happening-right-now example)
Step 1: Who are they? Fill in those fields for name, age, gender, and - if applicable - race.
Step 2: How did their life go? Fill in the bio.
Step 3: How do they act today? Type up a personality. (can be done before step 2)
Step 4: Anything else? Fill those in.
Step 5: Post it. Done just like that :)[/hider]

The site has a fair few procrastinators, so as long as you don't wind up in an RP where [i]everybody[/i] procrastinates, you should be fine.