And you lose.
Think of it like having a good card at a poker table and waving it around smiling so that everyone knows. If you let your emotions control you, you'll get fucked. It works in every aspect of life. Let a newly met girl know you're totally in love and she'll take advantage of you, make you pay for everything for a while and get bored quickly. Let a seller know you love the merchandise and he'll bring the price up.
Whenever you lose faith, do the math. Read about the asset, think of points for and against selling, watch some smart people on youtube like Andreas Antonopoulos, Barry Silbert, Tom Lee, and others.