Strength is the highest value of stress that a material can hold. If a material gets a stress above this limit, the material will break. How do we know the strength of the material? By doing laboratory testing, we can understand this value.
And what is stress? technically, stress is the quantity of load divided by perpendicular area of material that receives the load. The higher the load, the higher the stress. The smaller of the area, the higher the stress value. How to reduce the stress of material to avoid a material break? simply increase the area or decrease the load.
Your strength is the highest value of work stress that you can hold. If you get a work stress above this limit, then probably you will be “break”. Unfortunately, you can not do laboratory testing to find out this limit. You can only feel it. You can push your self to this limit to feel the “break”.