I already touched on this earlier. But it's such a key point that I want to elaborate on it. I'm talking about the need to get to alpha - a mental state when you are alert and awake, yet very calm, very relaxed.
For all serious IM/LOA exercises, this is the state you aim to be in, before you commence the IM/LOA exercises. The deeper you get into alpha, the more powerful your manifestation will be.
Getting to alpha consistently, quickly, regularly is a skill that you'll get better at, over time, and with practice.
There are different ways to get to alpha. Here are a few examples:
Progressive Muscular Relaxation (based on relaxing the muscles)
YouTube - Breathing Relaxation Exercise (based on breathing)
How to Perform Self Hypnosis - wikiHow (see just Steps 1 to 6)
Do practise the above. Note: even if you have no particular intentions to manifest, the exercises are all good for relaxing yourself and de-stressing.