Your actually right. Here's an old post of mine on the subject
Spells usually tend to affect the outcome of events or how people percieve them. For example, you can't change your appearance, but you can make it easier to find clothes that make you look nice, or to have people overlook flaws, etc.
You can't make a speed spell, but you can make a spell that improves the quality of your morning runs or gives you the will power to exercise.
A good way to check if magic will work is:
Can it happen on its own even if it's unlikely?
Does it avoid messing with free will?
(This may not be true for every magical discipline, but in my case spells work better if they have altruistic ends even if they primarily help you).
Let's use love spells as an example
Example of a spell doomed to fail:
Mind control used to make a specific girl, let's call her Ashley, who thinks you're an ugly creeper, fall into bed with you tomorrow
Spells that might work:
Spells that attract a girl who's life would be made better by being with you (even by a little) and who would brighten up your life. She can chose to not be with you, or even not to talk to you.
A spell that gives you the wisdom to communicate with others and understand them in a constructive way. THis is sort of a roundabout love spell for failing relationships, but it doesn't do anything crazy or affect free will. It might even help you both understand that the relationship needs to end
A spell that gives people around you the wisdom to overlook shallow things like appearances and focus more on personality. Again possible, helpful to everyone, and doesn't affect free will. If your personality is garbage, noone will want you.