A procrastinator is someone who always waits to do things. "I really need to pay this bill, but I've been procrastinating." "Recovering procrastinator" is a half-joke. It sounds like "recovering alcoholic." The speaker is saying procrastination is an illness that can be conquered, and that he is conquering it. "Hold myself up" means "Be a model," "Be a good example." You hold something up so that a group can see it. The writer is joking and saying "Look at me. I am showing myself to you. Not so that you can see a good example, but as a warning."

Recovering - To regain balance, strength. Procrastinator - Someone who puts things off for another time, delays things. Recovering procrastinator - Someone who has decided to stop delaying their own progress and is in the process of taking steps to do so. "Holding myself up" in this case means presenting oneself. So they are saying they are more comfortable presenting themselves to you as someone who would warn you from procrastinating, rather than someone who should motivate you.

A recovering procrastinator is a person for whom procrastination (laziness) is a disease, and that they are healing (recovering) from this condition. The expression is a joke, and has a similar to "recovering alcoholic". "Holding myself up" in this context means presenting myself as if I am an expert or a person you should respect. In this sentence, the writer is saying they are not worthy of being respected for that action/reason.