Reality and common sense > sentimental value or money+ blood, sweat, and tears....
At some point reason should take precedence over what you feel your car is worth because of all the "investments" you have made....I would imagine that most everyone knows that adding enhancements to most cars ( notice I said most) doesn't equate into added value. More often than not, mods bring down the resale of a car, in relation to retail value.