Starting a composition is a difficult task. Getting your inspirations, thinking creatively, applying your creative thoughts to your music and supplementing your ideas with additional composition are all difficult tasks to accomplish.
For starters, your current state of mind will greatly affect the music you write whether you feel angry, joyful or sad chances are your musical composition will in some way reflect this mood.
Different times of day and different seasons affect your composing as well as current affairs and any stresss you might have.
The variety of factors that can influence your composition periods are immense and hopefully these few pointers will demonstrate some methods of breaking out of the psychological restraints placed on you.
Colours If you are looking to compose a piece of music based around a certain mood find a relevant colour that matches for instance orange gives the impression of energy and drive. Eventually you will learn to bias your mood to suit the composition you are aiming for.
Character it is well known for actors to really get inside the character they are portraying through their acting. Understanding key emotions and various behaviours help the actors live as their proposed character. If you are creating a theme for a character (think darth vaders theme tune) you need to be demonstrating and describing that character through sound. If you follow the same process as an actor would you will eventually unravel hidden details that will help refine your composition, make it more realist and detailed and allow for it to be much more creative and expressive.
Nature a lot of creativity and inspiration can be got by observing nature. From birds communicating through a song like speech to the rustle of leaves in a summer breeze. Trying to emulate nature is an excellent way to begin a sound-scope or incorporating nature into a character theme for example to express an angelic quality, singing like the birds (fast trills on piccolo or glissandos on the violin)
Memories another great source to tap into is your memories. A lot of emotion will go into compositions that are personal in some way to yourself. Spend a few minutes reflecting on your past try to imagine the memory in great detail sounds, smells, colours the weather anything that will give you a good image and story to compose about.
A rugby player could develop his passing techniques and his scrum techniques but if he doesnt know the rules of the game he wont be able to perform during a game.