Perhaps God is allowing you to tire and weaken, (simply put,) because it is the only way that you will ever become strong.
"And He said to me, 'My grace is sufficient for you, for My strength is made perfect in weakness.' Therefore most gladly I will rather boast in my infirmities, that the power of Christ may rest upon me. Therefore I take pleasure in infirmities, in reproaches, in needs, in persecutions, in distresses, for Christ's sake. For when I am weak, then I am strong." - II Corinthians 12:9,10
The secret of filling is emptying, and so God's greatest vessel that he will ever use, will be the one which is the most vacant of it's own resources, so that a proportionable space is thereby made for God's resources that are, to take the place of yours which are not. If God has allowed a wearying or draining period in your life, and if that condition is not connected with a physiological cause, then it may be spiritual in nature. I personally believe that much hindrance has been wrought upon the Christian Church in general, by the belief that all true believers are filled with the Holy Spirit at the same time that they are sealed or indwelt by that same Holy Spirit. I don't believe it! Now this isn't a place to debate the subject, but I find both personal, christian associate, and New Testament evidence that one can indeed be filled with the Holy Spirit subsequent to their initial sealing of the Spirit at the time that they were converted. Man is a trichotomy by way of construction, and the Holy Spirit's relevance to both the human spirit, the human soul, and the human body are 3 different things. He, (the Holy Spirit,) indwells your spirit faculty with his person, and that speaks of life. Then, the Holy Spirit fills your soul with his holy influence, and that speaks of sanctification. Then, the Holy Spirit pours out upon your body his anointing when and as needed, and that speaks of service.
Because you are indwelt in your spirit by the Holy Spirit, his presence there proves your pardon and justification before God the Father through the Mediation of God the Son. Now, because you are legally holy through this mediation of Christ, you become the kind of person that God would properly have reason to make practically holy, and that is why sanctification must necessarily follow justification. Then, if because God has justified you and thereafter had proper reason to sanctify or make you relatively holy in a practical sense, he then has further reason to anoint you with power for his service, for that outpouring of the Holy Spirit upon your body for service would then be ideal, for you would experience his mighty power and blessings upon your sanctified services, which blessings then would not destroy you. Success is a far more dangerous thing than failure is, but a sanctified believer has already learned to die to their own strength and cultivate humility and selfless, outgoing Christlike love by practice, and so the outpouring of God's power and anointing will not inflate such a humbled and holy saint, whereas an anointing poured out upon an unjustifed and unsanctified person, (as in the case of Balaam the prophet, Caiaphas the high priest, Judas Iscariot, or those in Matthew 7:22 who were empowered to cast out demons, preach the gospel, work mighty miracles, and yet heard those terrible words, "I never knew you!" Why did Christ say that he didn't know them? They lacked the sanctification that would have evidenced their justification, for Christ said, "...depart from Me, you who practice lawlessness!" of verse 23. As Christ didn't know them, they correspondingly didn't truly know him, and that is why they didn't live holy lives, for they never had an inner union with the Christ who is the source of all righteous fruit in the Holy Spirit. So in the case of these particular anointed persons, the anointing that they had worked against them, as it was not preceeded by the primary work of pardon, justification and indwelling of the Holy Spirit, that work then to be followed by the filling of the Holy Spirit within their souls for the purpose of holiness in sanctification.
If you need power in your life, look upon your present weakness as God's way of telling you that you must find new strength in a new way that you have yet untapped, and yet this new strength is not to be considered more of the Holy Spirit's person, but rather more of the Holy Spirit's work. To know this "upon" power in your life, first cultivate holiness in sanctification, for God the Father having the dearest, kindest and most considerately wise plan for you, would not pour out such an empowering upon you that would not benefit you in eternity to follow, as it has some. There is new power indeed, but God greatly desires to pour out the power of the Holy Spirit upon children who are being progressively made holy in practice by that same Holy Spirit's influence in their souls, from his innermost position of his divine person indwelling their human spirits. There is a profound but necessary order in advantageously finding God's all sufficient power poured out upon your life, and I hope this helps you to find that power to soon fill the place of your present, but providentially helpful, weakness.
