To be a muse requires that you be more unhinged than the artist for whom you are inspiration.
And you must not care.
That much said, it is impossible to become a muse when one desires that end. Part of the secret of the muse is that you do not want this chain around your neck. You do not want to be responsible for your pain, sorrow, love, hate, fear, weakness and strength becoming an inspiration through your personage to a person you love in a way that cannot be reconciled with their mortal existence and your own.
The existence of the muse is tentative, at best. The artist, you see, is by nature more inspired by darkness than by light. Therefore, to give said artist love and support just does not work. You become a valuable part of said artist's existence but you do not become a muse.
The muse must, by nature, despise his or her very existence. The perfect muse requires that the artist validate its existence. All the madness and the failures and the incompatibility with life as we know it must be validated. The stable individual who desires such an existence is not qualified. The perfect muse is quite insane and quite unable to deal with life on a day to day basis.
Time passes quickly and situations change. The muse remains rooted in the causes that once were. The mystery of the muse can never be discovered. Life itself is at the cause and fulfillment is dangerous in the relationship. There must always be distance and apartness. There can never be peace in the valley. If there is, the muse runs the risk of destroying his or her power forever. And then the muse becomes nothing more than a companion and a lover, and the inspiration fades.
Consign yourself not to these chains. Muses are born and not made. The answer is within the path ahead. No one can become what they are not, just as no one can deny who they are. The muse is a self-destructive creature. It is the nature of the muse. Free yourself and become who you truly are. The shadows never lie.