In theory I certainly do believe in spiritual power (and want to exercise it); but I find it impossible consistently to believe it in practice (I lapse from that belief frequently); and this is a classic example of the mortal condition.
We can choose what we believe, and endorse; but we cannot always stick to that belief at all times. Therefore, what we are choosing is what we repent.
(In this instance, I repent my lapses from knowing - and behaving in light of that knowledge - that spiritual power is supreme.)
However, I reject the semi-technological idea of spiritual power that I quite often see among Christians - which seems to have it that the best way to influence the world is along the lines that to effect change one should organise prayer, especially mass prayer, to achieve specific material ends.
This I would regard as a materialist strategy. Material strategies - such as habits of prayer, or rituals - may assist the spiritual, probably have done, as some kind of generalisation, in some eras and situations; but there is no causal connection at the specific level - and nowadays (in our context) this reduces the spiritual to the material, reduces spirituality to a mechanism.
But if, instead, we regard spiritual power as of vast power, vast scope, capable of massive effects - but genuinely spiritual; then we can see that it is not really a 'power' at all. Power might be defined in terms of imposing our will; and this is not allowed, not possible, unless and until our will is wholly-aligned with creation.
For most people - this alignment is only sporadic and short-lived. During these times we can, I believe, indeed participate in God's work of creation; and therefore exercise real spiritual power. However, that which we most 'want' is not necessarily or usually that which is aligned with unfolding creation.
In a nutshell; only when we want Good are we personally able to exert spiritual power; but in those circumstances we can.
Therefore if we 'want' more spiritual power; we first must come to want what is Good.