A strong body can accomplish much but a iron will can reshape the world, its not a question about trying to do it nor is it a question about forcing it, i personally considers spells a triviality, just like martial artists train to make their bodies into weapons, a magicians highest aim is to make his mind into a weapon in such matter that he should be able to get and do what he desires without having to waste time on trivialities such as spells and rituals or waving a wand around.
a spell can achieve much but being able to work with the raw energy itself is much more rewarding.
My suggestion for you is to meditate, get in contact with the energy, focus on different body parts and as you focus on them you will become aware of the energy in them, it will feel like a small electric pulse or like a tickling, or perhaps you will feel how the part gets warm or cold, the feeling is different for each individual, since you seem to lack faith and self confidence this will atleast serve to prove your capabilities and show you that it aint very hard to accomplish small feats with energy.
Everything in this world is energy, energy is directed with thoughts thus it is in your best interest to first learn to feel and direct with your mind to gain understanding.
After all, spells are means to sub conciously start a process that over time will achieve the desired effect, consider it like picking up a bottle, write a note with your desires, put it in the bottle and throw the bottle into a sea and then return to your daily trivialities, it may be quick or it may take some time but sooner or later it?ll kick in, this is the most simplified explanation regarding spells that i can think of.
It is quite simple yet its human nature to complicate matters into eternity and beyond because their minds cannot understand the simplicity, dont push yourself, nothing can be gained by forcing it, follow the flow and be natural, you will succed sooner or later.
The sole act of meditation should be proof enough that you got the will power to succed and thats all that is needed.