Sankalpa should include the desire which you see as giving a meaning to your life, the high level of truth and self-realization. You should avoid intentions concentrating on irrelevant materialistic possessions of the outside world and pick a guiding goal, meaningful and significant.
Your resolve is seen by the mind as the statement of the truth, the factual information. It may sound unnatural, but your resolve should be stated in the present tense, reinforcing that what you strive to achieve is a fact, not a wishful future. The same logic underlies the affirmations which are done in a wakeful state. When these are stated in the yogic sleep, they become much more powerful.
You should keep your resolve in mind at all times. From the moment you commit to it, each action you take will either bring you closer to your desired state or will move your backward. Your choices are the ones that decide on how fast you can grow the plant out of the seed.